Frequently asked questions

Most common questions

  1. John Wood serial numbers contain a lot of information, including when the heater was manufactured. This can be determined by looking at the first four numbers, ignoring any letter that may start the serial number. The first two numbers represent the year the heater was built. If your heater was built before 2008, the next two numbers represent the month. If your heater was built after 2008, the next two numbers represent the week.

    For Example
    Serial number: U0106413635
    This heater was manufactured in June 2001

    To see if your water is still under warranty click here to go to our warranty validation page.

    Please note that warranties are based on use in residential applications.
    Reduced warranty for commercial applications.


  2. The most common reason a T&P valve is dripping water is thermal expansion. The water in a water heating system expands when it is heated and has a greater volume.

    Follow these easy steps to diagnose thermal expansion:

    • Turn the heater thermostat all the way down, and install a water pressure gauge with dead hand on the drain valve. Open the drain valve, so the gauge reads system pressure.
    • Open a hot water tap and allow 15% to 20% of the tank’s volume to run out.
    • Shut off the drain valve and make sure that no other fixture in the system, hot or cold, is open. Make sure that outside fixtures, if they are on the same system, are turned off too.
    • Check the water pressure gauge, and turn the pointer so it lines up with the pressure indicating needle. Turn the thermostat back up to its normal position, so the heater cycles on. Watch the pressure gauge.
    • If the system is closed, the pressure will start to climb steadily and rapidly. A small amount of thermal expansion control may be built into the system because of trapped air pockets or a water hammer arrestor. In that case the pressure will increase slightly, hold steady for a short time and then rapidly increase.
    • The temperature and pressure relief valve (T&P) or PRV should open and release water once the pressure reaches the maximum setting on the valve. The valve will close once the pressure falls below the pressure setting of the valve.
    • The PRV is installed between the check valve and the water heating system. The expansion tank is installed between the PRV and the water heating system. Follow the manufacturer’s instructions for installing the expansion tank.
    • Run the thermal expansion check again. The pressure should increase only slightly then hold steady throughout the recovery cycle. The expanded water is flowing back from the heater and into the pressurized storage bladder of the expansion tank. Air pressure will force this water out of the expansion tank into the supply once usage resumes.

    WARNING: Thermal expansion of water, if not compensated for in system design, will lead to the early failure of components. These failures are not covered by the manufacturer’s warranty, so it is extremely important that everyone be aware of the causes, symptoms and solutions to thermal expansion in a closed water heating system.

    How to install a pressure-reducing valve and expansion tank.

    The ideal fix involves the use of a pressure reducing valve, if supply pressures are above 60 to 70 psi, and a properly sized expansion tank.

    DO NOT DEPEND ON THE T&P VALVE TO HANDLE THERMAL EXPANSION! The T&P valve, according to the makers of those valves, was designed as an emergency relief device only. The T&P could be subject to reduced effectiveness or failure.


  3. Water accumulating on the floor or in the drain pan is generally caused by one of the following conditions:

    • Condensation
    • Drain valve leaking
    • Temperature and pressure relief valve leaking
    • Leak from piping on and near the inlet and outlet
    • Leak at gas valve threaded connection (gas models only)
    • Leak from gaskets for electric elements (electric models only)
    • Leak in heater tank

    CONDENSATION: Condensation should only be noticeable after a long draw of hot water. Once the temperature of the tank is above 110oF, condensation should stop.

    DRAIN VALVE LEAKING: Check to see if the heater drain valve is closed tightly. If the leakage cannot be stopped by the handwheel, replace the drain valve.

    TEMPERATURE AND PRESSURE RELIEF VALVE LEAKING: If the leakage is from temperature and pressure relief valve or its discharge pipe, it may represent relief valve activation. The relief valve relieves water slowly when actuating on pressure. A closed system can cause pressure to increase in the system. This condition is called thermal expansion. The incoming water pressure should also be checked and compared with the valve’s rating. If the supply water pressure is higher than the valve’s rating, a pressure reducing valve will be needed.

    LEAK FROM PIPING ON AND NEAR THE INLET AND OUTLET: In warm or humid locations, condensation can accumulate and run down flue tubes, cold water supply pipe, and heater connections. Check connections and fitting for possible leaks.

    LEAK AT GAS VALVE THREADED CONNECTION (GAS MODELS ONLY): Remove valve and reapply pipe joint compound.

    LEAK FROM GASKETS FOR ELECTRIC ELEMENTS (ELECTRIC MODELS ONLY): These gaskets can be replaced. The element threads may need to be resealed.

  4. Water heaters can often fail prematurely due to improper sizing. The storage capacities as well as the recovery rate are both important factors when sizing a water heating system. Improper sizing can also lead to complaints of not enough hot water. It is important to consider not only the volume of water required, but the temperature that is required. When a large volume of water is needed within a small amount of time, this water is generally supplied from storage. This volume is referred to as the dump load. When choosing the appropriate storage tank size, the actual and usable storage will need to be addressed. If water is required at a certain gallon per minute rate, this water will generally be supplied by the recovery of heater. Keep in mind that any dump loads also need to be included in this recovery.

    Some signs of an undersized water heater are:

    • Heavy condensation
    • Rust chips on the burners and flue tubes
    • Not enough hot water
    • Premature tank failure(s)
    When a water heater is properly sized, some condensation will occur. However, excessive condensation is not normal and will corrode the heater.
  5. The most common cause of smelly water is a bacteria that is already present in water, but grows rapidly when kept in a warm water environment such as water heaters or hot water storage tanks. This bacteria reduces sulfates that are also contained in the water to a point where they are converted into sulfides. Sulfides, when mixed with hydrogen produce an unpleasant rotten egg odor called hydrogen sulfide gas. Sometimes, hydrogen is already present in the water and is increased by the anode rod(s) found in your water heater.

    Permanently removing the anode rod(s) is not a suggested remedy as this will void your tank warranty.

    A solution for this problem is to chlorinate your water heater or hot water storage tank. A chlorine feeder may be the only permanent solution to iron or sulfur bacteria infestation. You can also try changing the anode rod from magnesium to aluminum.

  6. The use of water softeners in hard water areas and even moderately soft water areas is becoming a common occurrence. This practice has a potentially detrimental effect on the performance of the anode in the water heater which can cause a reduction in the life of the water heater. Customers using water softeners should expect more rapid anode consumption. Anodes should be inspected more often and replaced when nearing the end of their useful life.

  7. This is referred to as “water hammer”. Water hammer occurs in a piping system when water flowing through a pipeline is stopped abruptly. When water hammer occurs, a high intensity pressure wave travels back through the piping system until it reaches a point of some relief. The shock wave will then surge back and forth between the point of relief and the point of stoppage until the destructive energy is dissipated in the piping system. The violent action accounts for banging, thumping, and/or intense vibration in the pipeline. Although noise is generally associated with the occurrence of water hammer, it can occur without audible sound or noise. Quick closure always causes some degree of shock with or without noise. The common cause of water hammer is single lever faucets (sinks/lavatories) or automatic solenoid valves (dishwashers, washing machines, etc.). The speed of the valve closure time is directly related to the intensity of the surge pressure.

    The only effective means of control is to install water hammer arrestors. These devices have diaphragms which separate an air chamber from the water in the piping system. As the shock wave reaches this device, the air chamber absorbs the shock. Arrestors should be located as close as possible to the source of the shock wave.

  8. Condensate is the result of airborne water vapour being chilled below the dew point. The dew point is the temperature at which water vapour turns into liquid. Low incoming water temperatures cool the piping and the heat transfer surfaces of the water heater. When the main burner comes on, the hot flue gases turn into condensate upon contact with these surfaces. The typical home water heater will produce about one-half gallon of water vapour during every hour of operation. Condensate is often mistaken for leaking. Newer heaters will condensate more than older heaters because modern water heaters are much more efficient than their predecessors. The newer heaters utilize as much of the energy out of the main burner flame as possible. This lowers the flue gas and tank storage temperature and closer to the dew point temperature.

    To distinguish between a condensing water heater and a leaking water heater:

    1. Wipe up any water under the heater.
    2. Turn the knob on the thermostat to the pilot position.
    3. Wait 8 hours, check for water accumulation under the heater.
    4. Condensation should stop when the entire tank of water is heated above approximately 115 degrees

    If no water is found under the heater, the water heater was condensing.
    If water is found under the heater, check further for a loose fitting. If all fittings are tight and the tank is leaking, replace the water heater. Leaking heaters cannot be repaired.


  9. It is recommended that the tank be drained and flushed every 6 months to remove sediment which may buildup during operation. The water heater should be drained if being shut down for extended periods of time.

    GAS-FIRED WATER HEATER:

    To drain the tank, perform the following steps:

    • Turn off the gas to the water heater with the manual gas shut-off valve.
    • Close the cold water inlet valve.
    • Open a nearby hot water faucet.
    • Connect a hose to the drain valve and terminate it to an adequate drain.
    • Note: The drain hose should be rated for at least 94°C (200°F). If the drain hose does not have this rating, open the cold water inlet valve and nearby hot faucet until the water is no longer hot.
    • Open the water heater drain valve and allow all the water to drain from the tank. Flush the tank with water as needed to remove sediment.
    • Close the drain valve, refill the tank, and restart the heater as directed under “Operating Instructions”. If the water heater is going to be shut down for an extended period, the drain valve should be left open.
    • Important: Condensation may occur when refilling tank and should not be confused with a tank leak.
    • Turn off water supply.
    • If floor drain is not near water heater, connect a garden hose to drain valve and direct to floor drain.
    • To speed the flow of water, open a hot water tap to let air into tank at a single-handled faucet nearby.
    • Allow water to run until water is clear and no discolouration in water.
    • Turn drain valve off once water is clear.
    • Turn water supply back on. Fill tank with water.
    • Make sure tank is completely filled with water. Turn nearby faucet off.
    • Check for leaks.

    ELECTRIC WATER HEATER:

    NOTE: Make sure power is turned off in the case of electric heaters. Electric elements will burn out if they are operated in a dry tank.

    Turn off water supply.

    • If floor drain is not near water heater, connect a garden hose to drain valve and direct to floor drain.
    • To speed the flow of water, open a hot water tap to let air into tank at a single-handled faucet nearby.
    • Allow water to run until water is clear and no discolouration in water.
    • Turn drain valve off once water is clear.
    • Turn water supply back on. Fill tank with water.
    • Make sure tank is completely filled with water. Turn nearby faucet off.
    • Check for leaks.
    • Restore power.
  10. The element in your water heater could be one of four types: strap-on, plug-in, bolt-on (square flange) and screw-in. The water heater element should be visually inspected to ensure you are selecting the correct element.

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The element in your water heater could be one of four types: strap-on, plug-in, bolt-on (square flange) and screw-in. The water heater element should be visually inspected to ensure you are selecting the correct element.

The strap-on elements are heating bands that wrap around the water heater. These elements have been replaced by more efficient immersion type elements and have not been used in the manufacturing of residential water heaters since the 1970's. As a result, the elements are no longer being produced.

The plug-in elements are immersion-type elements and have a round flange that is held in place by a steel plate that bolts on to the water heater. A small rubber gasket (usually orange in colour) is used to seal the connection between the element and tank opening. These elements have not been used in manufacturing of water heaters since the mid 1980's; however, limited selections of plug-in elements are available for replacement parts.

The bolt-on (square flange) elements are immersion-type elements and have thick steel flange that bolts to the water heater. A thick black rubber gasket and a flat gasket are used to seal the connection between the element and the tank opening. The bolt-on elements are still used on some models of water heaters and are widely available.

The screw-in elements are immersion-type elements and have a hex head flange (1 1/2"). The element screws into the water heater and has a thin gasket that is used to seal the connection between the element and the tank opening. Plumber’s tape or pipe dope should be applied to the element threads.

All water supplies contain varying quantities of impurities, with calcium and limestone being the most prominent. When water is heated, these minerals "fall out" of the water and are deposited on the interior surfaces of the tank as scale. The formation of scale increases with the temperature of the stored water. Scale forms on all surfaces including the element itself. The scale builds up an insulating layer which impedes the efficient transfer of heat which may allow the element to glow red hot in specific localities along its surface.

When this occurs, the scale that has built up on the element surface will flake off. When water comes back in contact with the hot element surface, the water will flash into steam. This alternate heating and cooling of the element shortens its life span. This process also creates a layer of debris at the bottom of the tank which can build to considerable depths, even to the point where the lower element is covered, affecting the proper operation of the tank.

IMPORTANT:
To avoid risk of electric shock, make sure the power is turned off and remains off until all repairs have been completed.

WARNING:
A water heater is capable of producing hot water at a temperature sufficient enough to cause scalding injury. Take proper precautions when draining a water heater to prevent scalding injury.
Read all instructions carefully before repairing a water heater.

  1. Turn off water supply and power supply.
  2. Drain tank to a level below the element opening.
  3. Remove outer casing service door and fold back insulation.
  4. Disconnect wires from element and remove element bolts.
  5. Remove element and old gasket from the tank.
  6. Clean tank flange surfaces of any dirt or debris.
  7. Insert new gasket, element and thermostat bracket.
  8. For square flange (4-bolt) tighten element bolts diagonally a little at a time. Do not over-tighten or damage will occur.
  9. Insert thermostat behind the element bracket. Make sure thermostat is tight against tank. If necessary, bend the clips to provide more tension.
  10. Fill tank completely with water. Open a hot water faucet to let the accumulated air escape.
  11. Reconnect the wires to the element terminals. Consult the wiring diagram for proper connections.
  12. Check for leaks. Repair if necessary.
  13. Replace insulation over thermostat and element.
  14. Replace service door and turn on power supply.

When power is initially turned on to the unit, the upper element is energized and heats the water in the upper third of the tank.

When the upper third of the tank is heated to the upper thermostat, power is switched to the lower heating element. The lower element continues to heat until the water temperature in the lower portion of the tank is heated to the lower thermostat setting.

As hot water is drawn from the top of the tank the dip tube delivers cold water to the bottom of the tank.

Eventually the cold water mixes with the hot, lowering the temperature below the thermostat setting and the bottom element is energized. If enough water is drawn to cool the upper-third of the tank, the upper thermostat will send power to the upper element first. When the upper-third of the tank is heated, power will again be switched to the lower element. If the upper element burns out, the water heater will cease to function because the upper thermostat will never be satisfied and power will never be switched to the lower element. If water temperature in the tank reaches 180°F, the manual reset hi-limit switch will be tripped. This switch can be reset by firmly pushing the red button above the upper thermostat.


If enough water is drawn to cool the upper-third of the tank, the upper thermostat will send power to the upper element first. When the upper-third of the tank is heated, power will again be switched to the lower element. If the upper element burns out, the water heater will cease to function because the upper thermostat will never be satisfied and power will never be switched to the lower element. If water temperature in the tank reaches 180°F, the manual reset hi-limit switch will be tripped. This switch can be reset by firmly pushing the red button above the upper thermostat.

Single-element water heaters have one element mounted at the bottom of the tank controlled by a single thermostat and high limit switch.

The water heater temperature is shipped with both thermostats factory preset at 140ºF, unless specified differently by federal or provincial regulations. The equipped adjustable thermostats on your water heater have a linear relationship between degrees of angular rotation and the corresponding change in temperature. Thus, rotating the temperature adjustment indicator 30 angular degrees will result in a 10ºF change in the water temperature.

Follow these steps when adjusting the temperature:

  1. TURN OFF THE ELECTRICAL SUPPLY. Do not attempt to adjust thermostat(s) with the power turned on.
  2. Remove the thermostat access panels and foam covers from the thermostats. Do not remove the plastic personal protectors covering the thermostats.
  3. Using a flat tip screwdriver, rotate the adjusting knob to the desired temperature setting.
  4. Replace the foam covers and access panels, and turn on the heater’s electrical supply

  1. Turn the power to the water heater off at the main electrical panel.
  2. Remove the two access panels from the front of the water heater.
  3. Turn the power to the water heater back on. CAUTION: You will be testing a live circuit.
  4. With a multimeter, turn the setting to AC voltage, 240v or higher.
  5. Test between #1 & #2 of the high limit, you should have a reading of 240v. If the reading is “0” there is a problem with the electrical panel, in which case call an electrician.
  6. Test between #3 & #4 of the high limit, you should have a reading of 240v, If the reading is “0” try pushing the red re-set button on the hi-limit you should now have 240v, if not then change thermostat/limit.
  7. If the upper portion of the water heater is cold, test if T&P valve is cold, you should have 240v between #7 of the upper thermostat and #4 of the hi-limit.
  8. Considering all tests between 5 & 6 are good, you should have 240v across the two screws “A” & “B” of the upper element when the tank is cold.
  9. If the tank is hot, test the power across #6 of the upper thermostat and #4 of the hi-limit you should have 240v. If not, change the thermostat. Upper portion of the heater should be hot. The lower portion of the tank is the part of the tank that gets the most work; this element will be the first element to come on when there is a demand for hot water.

You will always have 240v between #1 and #4 on the hi-limit. 240v between screws “A” and “B” on the upper element when the tank is COLD. 240v between screws “C” and “D” on the lower element when the upper portion of the tank is HOT. When the tank is SATISFIED you will have 240v between screw #6 of the upper thermostat and #4 of the hi-limit but not power across the elements. With a short draw of hot water the lower thermostat will close and send the power to the opposite side of the element to heat up. If all voltages test OK, turn off the power to the water heater at the main electrical panel, remove wire from one side of each element, set the multimeter to “Ohms” and test the ohms reading of the elements.

If the ohms reading is too low or too high, change the element.
1200w @ 120v = 12.0 ohms
1500w @ 120v = 9.6 ohms
1500w @ 240v = 38.4 ohms
3000w @ 240v = 19.2 ohms
3800w @ 240v = 15.2 ohms
4500w @ 240v = 12.8 ohms
5500w @ 240v = 10.5 ohms

Condensate is the result of airborne water vapour being chilled below the dew point. The dew point is the temperature at which water vapour turns into liquid. Low incoming water temperatures cool the piping and the heat transfer surfaces of the water heater. When the main burner comes on, the hot flue gases turn into condensate upon contact with these surfaces. The typical home water heater will produce about one-half gallon of water vapour during every hour of operation. Condensate is often mistaken for leaking. Newer heaters will condensate more than older heaters because modern water heaters are much more efficient than their predecessors. The newer heaters utilize as much of the energy out of the main burner flame as possible. This lowers the flue gas and tank storage temperature and closer to the dew point temperature.

To distinguish between a condensing water heater and a leaking water heater:

1. Wipe up any water under the heater.
2. Turn the knob on the thermostat to the pilot position.
3. Wait 8 hours, check for water accumulation under the heater.
4. Condensation should stop when the entire tank of water is heated above approximately 115 degrees:

If no water is found under the heater, the water heater was condensing.
If water is found under the heater, check further for a loose fitting. If all fittings are tight and the tank is leaking, replace the water heater. Leaking heaters cannot be repaired.

If the water coming out of your heater is not hot enough there could be a few different issues. Some of these will require work to be done by a certified HVAC technician.

  • The temperature could be set too low. When the unit is shipped out it will be set at 120°F. Check what the water temperature is set at by looking at either the LCD display on the front of the unit. If there is no LCD refer to the remote included with the heater.
  • Check for cross plumbing between cold water lines and hot water lines. To do this, turn off the cold water supply and turn on a hot water fixture. The water at the fixture should eventually completely stop flowing. If water continues to run you have crossed plumbing and should contact a plumber.
  • Unit may be hard water scaled. The scale acts as an insulator preventing the heat exchanger from transferring heat to the water. Refer to your installation manual for descaling procedures.
  • The unit may not be receiving enough gas. There are a various reasons this could be happening. Contact a certified HVAC technician.
  • If the LCD display on the front of the heater or your remote has a flashing 101 it means there is a 101 error code. A 101 error code indicates there is a combustion issue and you should contact a certified HVAC technician.
  • Check for dust, debris or anything in the venting outside your house and inside the unit itself. If there is debris in the venting you may be able to safely remove it. If there is dust inside the unit, there will also be dust inside the burner and heat exchanger. Contact a certified HVAC technician.

If the water temperature fluctuates while the water is running there are a few possible issues.

  • Check for cross plumbing between cold water lines and hot water lines. To do this turn off the cold water supply and turn on a hot water fixture. The water at the fixture should eventually completely stop flowing. If water continues to run you have crossed plumbing and should contact a plumber.
  • The filter on cold water inlet should be clean; look for signs of hard water scaling. If found Refer to your installation manual for descaling procedures.
  • On well systems or even on some city water systems, water pressure fluctuations (especially on low flow) of 8 to 10 psi will result in flow rate fluctuations, which will in turn result in minor temperature fluctuations.
  • There could be an issue your gas supply or venting. Contact a certified HVAC technician.

If the heater was just installed it may have been installed incorrectly. If this is not the case there may be an issue with the flow sensor, which will require a certified HVAC technician. Alternately, the filter may need to be cleaned.

To clean the filter, the unit must first be drained:

  • Close the manual gas shut off valve.
  • Turn off power to the unit, and then turn on again.
  • Wait 30 seconds, and then turn off power to the unit again.
  • Close the cold water inlet shutoff valve.
  • Open all hot water taps in the house to remove the initial pressure.
  • When the residual water flow has ceased, close all hot water taps.
  • Unscrew the drain plugs (hot water outlet drain plug and cold water inlet filter) to drain the remaining water out of the unit. Have a bucket or pan to catch the water from the unit’s drain plugs.
  • Wait a few minutes to ensure all water has completely drained from unit.
  • Check the water filter located within the cold inlet.
  • With a tiny brush, clean the water filter of any debris which may have accumulated and reinsert the filter back into the cold water inlet.
  • Securely screw the filter

It is common that a tankless unit will require more time for hot water to arrive at the faucet. The time it takes to deliver hot water to your fixtures depends on the length of piping between the two. The longer the distance or the bigger the pipes, the longer it will take to get hot water. If this is the case and you would like to receive hot water to your fixtures quicker, you may want to consider a hot water recirculation system. If you already have a recirculation system there may be an issue with it and you should contact a certified HVAC technician.

The most common cause of smelly water is a bacteria that is already present in water, but grows rapidly when kept in a warm water environment such as water heaters or hot water storage tanks. This bacteria reduces sulfates that are also contained in the water to a point where they are converted into sulfides. Sulfides, when mixed with hydrogen produce an unpleasant rotten egg odor called hydrogen sulfide gas. Sometimes, hydrogen is already present in the water and is increased by the anode rod(s) found in your water heater.

Permanently removing the anode rod(s) is not a suggested remedy as this will void your tank warranty.

A solution for this problem is to chlorinate your water heater or hot water storage tank. A chlorine feeder may be the only permanent solution to iron or sulfur bacteria infestation. You can also try changing the anode rod from magnesium to aluminum.

This problem will rarely occur as a result of a water heater or storage tank. Rusty coloured water is caused by the water coming in contact with bare metal. In order for this to happen, a lining failure would have to be so significant that it would allow the water to come in contact with enough bare metal to discolour the contents of even a small tank. Fortunately, with today's high quality glass-lined tanks, this is a very rare occurrence. Instead, the common cause of rusty coloured water is bacteria that reduces the iron found in water. This bacteria is found in soil, water wells, water treatment plants and water distribution piping systems. The bacteria feeds off this soluble iron and, if not treated and allowed to flourish, will result in stained laundry, tablewear and plumbing fixtures. If this bacteria exists in your heater or tank, you may require new anode rod(s), as they will fail prematurely in these conditions. To solve this chlorinate your water heater or hot water storage tank.

Gases such as oxygen, chlorine, carbon dioxide, hydrogen sulfide, and others are soluble in water. As the pressure increases, the amount of gas that water can hold in a solution decreases which cause the cloudy effect. "Milky" water caused by dissolved gasses can be greatly reduced with aerated faucets

The use of water softeners in hard water areas and even moderately soft water areas is becoming a common occurrence. This practice has a potentially detrimental effect on the performance of the anode in the water heater which can cause a reduction in the life of the water heater. Customers using water softeners should expect more rapid anode consumption. Anodes should be inspected more often and replaced when nearing the end of their useful life.

It is recommended that the tank be drained and flushed every 6 months to remove sediment which may buildup during operation. The water heater should be drained if being shut down for extended periods of time.

GAS-FIRED WATER HEATER:

To drain the tank, perform the following steps:

  • Turn off the gas to the water heater with the manual gas shut-off valve.
  • Close the cold water inlet valve.
  • Open a nearby hot water faucet.
  • Connect a hose to the drain valve and terminate it to an adequate drain.
  • Note: The drain hose should be rated for at least 94°C (200°F). If the drain hose does not have this rating, open the cold water inlet valve and nearby hot faucet until the water is no longer hot.
  • Open the water heater drain valve and allow all the water to drain from the tank. Flush the tank with water as needed to remove sediment.
  • Close the drain valve, refill the tank, and restart the heater as directed under “Operating Instructions”. If the water heater is going to be shut down for an extended period, the drain valve should be left open.
  • Important: Condensation may occur when refilling tank and should not be confused with a tank leak.
  • Turn off water supply.
  • If floor drain is not near water heater, connect a garden hose to drain valve and direct to floor drain.
  • To speed the flow of water, open a hot water tap to let air into tank at a single-handled faucet nearby.
  • Allow water to run until water is clear and no discolouration in water.
  • Turn drain valve off once water is clear.
  • Turn water supply back on. Fill tank with water.
  • Make sure tank is completely filled with water. Turn nearby faucet off.
  • Check for leaks.

ELECTRIC WATER HEATER:

NOTE: Make sure power is turned off in the case of electric heaters. Electric elements will burn out if they are operated in a dry tank.

Turn off water supply.

  • If floor drain is not near water heater, connect a garden hose to drain valve and direct to floor drain.
  • To speed the flow of water, open a hot water tap to let air into tank at a single-handled faucet nearby.
  • Allow water to run until water is clear and no discolouration in water.
  • Turn drain valve off once water is clear.
  • Turn water supply back on. Fill tank with water.
  • Make sure tank is completely filled with water. Turn nearby faucet off.
  • Check for leaks.
  • Restore power.

Glass-lined water heaters are supplied with sacrificial magnesium anode rods that protect the interior of the tank through cathodic action. As the rod works, it slowly dissolves over time and must be replaced when it is totally consumed.

ANODE ROD INSPECTION INSTRUCTIONS:

  • Locate the anode rod on top of the water heater. It is accessible through the hole closest to the center of the tank. There will be insulation covering it and there may be a plastic cap over the access hole. The anode rod has a 1 1/16th inch hex head.
  • Turn off the power if electric. If gas, turn valve from “on” to “pilot” on the water heater.
  • Turn off the cold/inlet water supply to the heater.
  • Drain off approximately 5 gallons of water from the unit.
  • Using a 1 1/16th socket wrench, remove the anode rod. (It could be well tightened from the factory.)
  • Inspect anode rod for consistent pitting. If pitting is consistent and thicker than 3/8” in diameter, reinstall rod. If rod is less than 3/8” in diameter, or bare inner core is exposed, other than at each end, replace anode rod.
  • Turn water supply back on and ensure the tank is completely filled up with water by opening all the hot water faucets in the house to release the air in plumbing system. Allow the water to run for three minutes before closing the faucets.
  • Turn the power back on, or turn the dial on the gas valve from “pilot” back to “on” depending upon your unit.
  1. Turn off the electrical switch or shut off main gas supply.
  2. Close the cold water inlet valve to the heater.
  3. Open a hot water faucet within the system to relieve tank pressure.
  4. Drain 2-5 gallons of water to allow the addition of bleach to the tank. Use a hose connected to the drain valve if an open drain is not adjacent to the heater. CAUTION: Water may be HOT.
  5. Remove anode rod or disconnect the hot water outlet pipe from the heater.
  6. Using a funnel in the anode rod or hot water opening, add one gallon of household chlorine bleach (e.g. Clorox, Javex ) for every 25 gallons of tank capacity. Re-pipe the heater.
  7. Reinstall anode rod(s) after inspecting and replacing as needed
  8. Open the cold water inlet valve at the heater and fill the tank with water. Then draw the water to every hot water fixture, until the smell of chlorine is detected. Operate dish and clothes washers until a noticeable amount of the chlorine is detected as well. All hot water lines must receive treatment.
  9. Close inlet valve and leave the bleach mixture in the system for a minimum of 2 hours.
  10. Drain the bleach mixture from the tank through the heater drain valve and close the heater drain valve.
  11. Open cold water inlet valve and completely fill the tank with fresh water. To ensure that the water heater is full of water and that all the air has been purged from the system, run all the hot water faucets in the house continuously for three (3) minutes. If you can still smell chlorine at the faucets run them until there is no longer any odour. Do not supply power to this water heater until you have verified that the unit is completely filled with water.
  12. Check for water leaks at all fittings used; repair as necessary.
  13. Turn on the manual electrical switch or gas valve and ensure tank is full of water to prevent dry-firing.

If an inspection of the filter shows a build-up of dirt or debris on the filter, it should be cleaned. The filter can be vacuumed to remove the build-up. Visually inspect the flame arrester by placing a mirror underneath the water heater. A flashlight can be used to illuminate the slots in the flame arrester if necessary. Routine cleaning of the flame arrester is recommended if the inspection shows accumulation of debris on the flame arrester.

Use a vacuum cleaner to remove all loose debris in the flame arrester. If necessary, a soft bristle brush can be used to dislodge any remaining debris.

  1. Turn off the power if electric. If gas, unplug and turn off the incoming gas supply to the water heater.
  2. Turn off the cold inlet water supply to the heater.
  3. Open a hot water faucet located nearby and leave it open. Turn off water supply to house if single handle faucets could be opened during this procedure.
  4. Open the drain and drain off approximately 5 gallons of water from the heater.
  5. Disconnect the cold water supply line from your water heater.
  6. Put a thick layer of rags around the threads of the cold water inlet nipple to avoid damaging the threads when you unscrew the nipple.
  7. Using a pipe wrench, unscrew the cold water inlet nipple-dip tube combination. A helper may be required to steady the heater.
  8. Inspect for damage, such as a split, crack or fracture; replace the dip tube if necessary. If dip tube is completely missing, check the hot water outlet to eliminate the possibility of mix-up at installation.
  9. Wrap threads of the new dip tube with white teflon tape or use teflon pipe dope (TPD)
  10. Install the dip tube into tank and tighten.
  11. Reconnect the cold water supply line to the heater.
  12. Turn water supply back on and ensure the tank is completely filled with water. Open a faucet to release air from the plumbing system.
  13. If electric turn the power back on; or if gas, turn on the gas supply to the unit and follow the lighting instructions on the side of the water heater.

John Wood serial numbers contain a lot of information, including when the heater was manufactured. This can be determined by looking at the first four numbers, ignoring any letter that may start the serial number. The first two numbers represent the year the heater was built. If your heater was built before 2008, the next two numbers represent the month. If your heater was built after 2008, the next two numbers represent the week.

For Example
Serial number: U0106413635
This heater was manufactured in June 2001

To see if your water is still under warranty click here to go to our warranty validation page.

Please note that warranties are based on use in residential applications.
Reduced warranty for commercial applications.

Insulation blankets available to the general public for external use on gas water heaters are not necessary with John Wood products. The purpose of an insulation blanket is to reduce the standby heat loss encountered with storage tank heaters. John Wood water heaters meet or exceed the National Appliance Energy Conservation Act standards with respect to insulation and standby loss requirements, making an insulation blanket unnecessary.

Piping in series can cause the first heater to fail sooner than the second as you are using the full capacity of the first heater and only upon an increased demand, is the second heater cycled on. The better choice is to pipe in parallel which allows you to use both heaters equally. It allows the system to act as one heater rather than independent. By drawing hot water out of both heaters equally, you are able to equalize the life of your heaters.


These noises are an indication of scale build-up that you will need to remove. The task can prove to be relatively easy if you follow the steps to complete the process properly.

  1. Turn off the heater.
  2. Drain the heater.
  3. Remove the anode.
  4. Create a solution of one part vinegar to one part water to a quantity that fills the heater to capacity.
  5. Turn the water heater back on and leave the solution to work for at least two hours.
  6. Drain the heater
  7. Once the cleaning solution has been completely drained, you must rinse out the heater.
  8. Fill the water heater with fresh water to its capacity and leave it for a few minutes before letting it drain. This is a process that must be repeated in order to ensure the water heater is properly rinsed.
  9. Replace the anode.
  10. The tank can then be refilled, turned on and used as normal.

The most common reason a T&P valve is dripping water is thermal expansion. The water in a water heating system expands when it is heated and has a greater volume.

Follow these easy steps to diagnose thermal expansion:

  • Turn the heater thermostat all the way down, and install a water pressure gauge with dead hand on the drain valve. Open the drain valve, so the gauge reads system pressure.
  • Open a hot water tap and allow 15% to 20% of the tank’s volume to run out.
  • Shut off the drain valve and make sure that no other fixture in the system, hot or cold, is open. Make sure that outside fixtures, if they are on the same system, are turned off too.
  • Check the water pressure gauge, and turn the pointer so it lines up with the pressure indicating needle. Turn the thermostat back up to its normal position, so the heater cycles on. Watch the pressure gauge.
  • If the system is closed, the pressure will start to climb steadily and rapidly. A small amount of thermal expansion control may be built into the system because of trapped air pockets or a water hammer arrestor. In that case the pressure will increase slightly, hold steady for a short time and then rapidly increase.
  • The temperature and pressure relief valve (T&P) or PRV should open and release water once the pressure reaches the maximum setting on the valve. The valve will close once the pressure falls below the pressure setting of the valve.
  • The PRV is installed between the check valve and the water heating system. The expansion tank is installed between the PRV and the water heating system. Follow the manufacturer’s instructions for installing the expansion tank.
  • Run the thermal expansion check again. The pressure should increase only slightly then hold steady throughout the recovery cycle. The expanded water is flowing back from the heater and into the pressurized storage bladder of the expansion tank. Air pressure will force this water out of the expansion tank into the supply once usage resumes.

WARNING: Thermal expansion of water, if not compensated for in system design, will lead to the early failure of components. These failures are not covered by the manufacturer’s warranty, so it is extremely important that everyone be aware of the causes, symptoms and solutions to thermal expansion in a closed water heating system.

How to install a pressure-reducing valve and expansion tank.

The ideal fix involves the use of a pressure reducing valve, if supply pressures are above 60 to 70 psi, and a properly sized expansion tank.

DO NOT DEPEND ON THE T&P VALVE TO HANDLE THERMAL EXPANSION! The T&P valve, according to the makers of those valves, was designed as an emergency relief device only. The T&P could be subject to reduced effectiveness or failure.

Water accumulating on the floor or in the drain pan is generally caused by one of the following conditions:

  • Condensation
  • Drain valve leaking
  • Temperature and pressure relief valve leaking
  • Leak from piping on and near the inlet and outlet
  • Leak at gas valve threaded connection (gas models only)
  • Leak from gaskets for electric elements (electric models only)
  • Leak in heater tank

CONDENSATION: Condensation should only be noticeable after a long draw of hot water. Once the temperature of the tank is above 110oF, condensation should stop.

DRAIN VALVE LEAKING: Check to see if the heater drain valve is closed tightly. If the leakage cannot be stopped by the handwheel, replace the drain valve.

TEMPERATURE AND PRESSURE RELIEF VALVE LEAKING: If the leakage is from temperature and pressure relief valve or its discharge pipe, it may represent relief valve activation. The relief valve relieves water slowly when actuating on pressure. A closed system can cause pressure to increase in the system. This condition is called thermal expansion. The incoming water pressure should also be checked and compared with the valve’s rating. If the supply water pressure is higher than the valve’s rating, a pressure reducing valve will be needed.

LEAK FROM PIPING ON AND NEAR THE INLET AND OUTLET: In warm or humid locations, condensation can accumulate and run down flue tubes, cold water supply pipe, and heater connections. Check connections and fitting for possible leaks.

LEAK AT GAS VALVE THREADED CONNECTION (GAS MODELS ONLY): Remove valve and reapply pipe joint compound.

LEAK FROM GASKETS FOR ELECTRIC ELEMENTS (ELECTRIC MODELS ONLY): These gaskets can be replaced. The element threads may need to be resealed.

This is referred to as “water hammer”. Water hammer occurs in a piping system when water flowing through a pipeline is stopped abruptly. When water hammer occurs, a high intensity pressure wave travels back through the piping system until it reaches a point of some relief. The shock wave will then surge back and forth between the point of relief and the point of stoppage until the destructive energy is dissipated in the piping system. The violent action accounts for banging, thumping, and/or intense vibration in the pipeline. Although noise is generally associated with the occurrence of water hammer, it can occur without audible sound or noise. Quick closure always causes some degree of shock with or without noise. The common cause of water hammer is single lever faucets (sinks/lavatories) or automatic solenoid valves (dishwashers, washing machines, etc.). The speed of the valve closure time is directly related to the intensity of the surge pressure.

The only effective means of control is to install water hammer arrestors. These devices have diaphragms which separate an air chamber from the water in the piping system. As the shock wave reaches this device, the air chamber absorbs the shock. Arrestors should be located as close as possible to the source of the shock wave.

Heat traps are installed on some residential water heaters to comply with the many utility incentive programs, and certain new construction or replacement product requirements in place throughout the country. Devices such as impulse sprinklers and water pumps can cause the pulsating. The noise is sometimes conducted through piping and framing of the house annoying the occupants.

Since there is no simple way to correct pulsation of the water supply, removal of the heat traps is sometimes the only practical alternative. The heat traps may be removed from the heater without affecting the safe operation of the heater.

The removal of the heat traps will cause a small reduction in the overall efficiency of the water heater.

The installation of a drain valve generally requires the draining of the tank. Make sure power is turned off in the case of electric heaters, or the gas control is turned to PILOT in the case of gas heaters. Electric elements will burn out if they are operated in a dry tank, and damage will occur if the gas burner comes on with a gas heater which is not filled with water.

  • Turn off water supply and power supply.
  • Drain tank. To speed the flow of water, open a hot water tap to let air into tank.
  • Remove existing valve.
  • Clean the tank threads of any dirt or foreign matter that might affect the proper thread sealing of the new valve.
  • Install new drain valve using a high quality thread sealant (either plumbers tape or approved pipe dope).
  • Fill tank with water and check for leaks. Make sure tank is completely filled with water.
  • Restore power.

Water heaters can often fail prematurely due to improper sizing. The storage capacities as well as the recovery rate are both important factors when sizing a water heating system. Improper sizing can also lead to complaints of not enough hot water. It is important to consider not only the volume of water required, but the temperature that is required. When a large volume of water is needed within a small amount of time, this water is generally supplied from storage. This volume is referred to as the dump load. When choosing the appropriate storage tank size, the actual and usable storage will need to be addressed. If water is required at a certain gallon per minute rate, this water will generally be supplied by the recovery of heater. Keep in mind that any dump loads also need to be included in this recovery.

Some signs of an undersized water heater are:

  • Heavy condensation
  • Rust chips on the burners and flue tubes
  • Not enough hot water
  • Premature tank failure(s)
When a water heater is properly sized, some condensation will occur. However, excessive condensation is not normal and will corrode the heater.

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