leaking water heater pressure relief valve

[jl]

I was told that you should periodically open the pressure relief valve on my hot water heater. Well I did and now it is dripping. It is too much to ignore. Do I replace the valve?, Try to flush it clean? Other suggestions?

[LazyPup]

Watts Corporation, which is the leading manufacturer of Temperature & Pressure Relief valves, recommends manually opening the valve at intervals of not more than once per year.

When the valve is manually opened the handle should be lifted to full open then allowed to snap back to the closed position. If the valve does not reseal you may try lifting it to the full open position and allowing it to snap closed two or three times. If it will not reseat after three times the valve should be replaced.

HOW TO REPLACE A WATER HEATER T&P VALVE:

1. For Gas water heaters, turn the burner control to the OFF position.
For Electric water heaters pull the electrical service disconnect or switch the electrical circuit breaker to the OFF position. (NOTE-If there is not a direct line of sight from the electric water heater to the circuit breaker panel an electric water heater is required to have a service disconnect in the immediate vicinity of the water heater.)

2. Turn the water heater cold water supply valve to the OFF position.

3. Some people try to change the valve on the fly without draining the water heater. While it can be done in that manner there is an extremely high risk of personal injury from scalding hot water. It is best to drain the tank. When draining a water heater it is important to open a hot water faucett at a high point in your hot water plumbing system to vent air into the lines, otherwise you will have a risk of the standing water staying in the pipes and spilling back on you while changing the valve. (Normally the bathroom lavatory bowl hot water faucett on the highest floor in the structure is the proper high point to vent the lines).

4.The T&P overflow line is connected to the T&P valve by means of a 3/4" male pipe thread adapter which is screwed into the T&P valve body. Remove the T&P valve discharge line from the valve. If your T&P discharge line is plumbed directly outside the structure removing may require cutting the line. If it is a copper line and requires cutting it is best to cut the line at least 1/2 down the height of the tank or lower. This will prevent heat from damaging the new line when you have to solder the overflow back in place.

5. Manually lift the T&P valve handle to insure the water has drained below the level of the T&P valve, then remove the T7P valve by turning counterclockwise with a medium sized pipe wrench (14" to 24" pipe wrench)

6. Apply 3 full wraps of RED (Triple density) PTFE (TEFLON) tape or a Non-Hardening type pipe dope to the threads of the new valve.

7. Use a 3/4" stainless steel fitting brush to clean the female threads of the fitting on the water heater vessel.

8. Insert the new valve into the water heater vessel and hsnd tighten, then use a pipe wrench to tighten in place. Do not lift the T&P valve test handle and be sure not to apply any stress on the test handle while tightening the new valve in place. When making your final turn be very careful to stop with the T&P discharge valve properly aligned to connect the overflow line. Absolutely do not reverse turn the valve to align it to the discharge line. Reversing a threaded pipe fitting WILL result in a leak.

9. Apply 3 full wraps of RED triple density teflon tape to the discharge line male thread adapter and screw into the discharge port of the T&P valve.

10. If you had to cut the T&P discharge line to remove it you should reconnect the line with a coupling and solder in place. (If it is a PVC line you also use a coupling and glue it in place.)

VERY IMPORTANT: the diameter of the T&P discharge line MUST BE equal to the diameter of the T&P discharge port. Absolutely do not reduce the diameter of the discharge line. Reducing a line diameter by one nominal trade size reduces the capacity of that line by 50% and in the case of a water heater T&P valve it could result in a water heater exploding.

11. Close the water heater drain valve.

12. Open the water heater cold water supply line and refill the tank and hot water system. Keep at least one hot water faucett open to vent excess air out of the system while refilling the water heater.

13. Reset the electrical circuit breaker or service disconnect or relight the gas pilot light.

14. You will need to open each hot water faucett in the structure to vent off any excess air in the lines. Expect a bit of sputtering as the air vents out. Once you have a full flow of water, close the faucett and move on the the next one.

15. Visually inspect the T&P valve to insure there are no water leaks.

NOTE: The ANSI (American National Standards Institute) has introduced new specifications for PTFE (Teflon Tape). The common single density white teflon tape found in most hardware stores is only certified for use on fittings up to 3/8" in diameter. For NPT (National Pipe Taper) threads and fittings greater than 3/8" but less than 2" we are required to us TRIPLE DENSITY teflon, and triple density is only approved if 3 full wraps are applied to the thread.

You may now find red triple density teflon tape at most Lowes, Home Depot's and larger hardware stores. If your local hardware does not carry it please ask them to consider adding it to their inventory.

[jl]

Thanks so much. There seem to be a wide range for T&P valves...Some cost $5 and others $45. Does it make a difference?

[LazyPup]

There are a number of different sizes of T&P valves. The ones most commonly used on residential water heaters are 3/4" mount with a 3/4" discharge port. Typically a quality WATTS T&P valve for a residential water heater should range in the area of $12 to $20.

When looking at T&P valves be sure the valve you select says TEMPERATURE AND PRESSURE. You will also see Pressure Relief Valves and Watts 210 Gas Shutoffs in the same are. In some instances when you such as when a water heater is installed in a basement below the lowest point of gravity drain and their is no sump we opt to install a WATTS 210 gas shutoff valve. The Watts 210 gas shutoff has a temperature sensing probe and if the internal temperature of the water heater exceeds 210degF it shuts off the gas supply to the burner regulator.

A Watts 210 gas valve must be installed in the upper 6" of the water heater storage vessel and the gas line must first be plumbed to the Watts 210 valve, then down to the water heater gas control.

When a Watts 210 gas shutoff is installed it is also necessary to install a "Pressure Relief Valve" at a convenient point that is above the gravity drain, or where it would permit running a gravity drain outside the structure. (Some local codes will also require and expansion tank on the cold water supply line when a Watts 210 gas control and a Pressure releif valve are installed.

T&P valves are rated by BTU's. If you will look at the tag attached to the manual lift handle you will see the BTU rating for your present valve. It is vitally important that you replace the T&P valve with a valve of the same BTU rating.