Water Heater Pressure Relief Valve Pipe Size

If a pressure relief valve for a boiler is accidentally installed on a water heater it will leak like crazy from the start.

Water heater pressure relief valve pipe size.

By code you have to run the same size as the opening which means the pipe needs to be 3 4 in diameter. Unscrew the overflow pipe from the tpr valve using a large adjustable wrench. There are several styles of tpr valve available including universal pressure relief valves. Therefore a water heater with a mawp of 160 psi still requires a t p relief valve set at 150 psi even though the vessel is designed and built to withstand a higher pressure.

Not terminate more than 6 inches 152 mm above the floor or waste receptor. This size valve will not work. A trapped tpr dischage pipe is a common defect when a replacement water heater s tpr valve is lower than the original one and the installer connects to the exisitng discharge piping at the wall. It s important to choose a replacement valve with the same btu rating and pipe size.

Model codes require the t p relief valve be set no higher than 150 psi. 8 termination of the tpr drain pipe cannot be more than 6 inches or less than two pipe diameters above the floor ground or waster receptor flood rim level. The tpr valve will activate if either water temperature measured in degrees fahrenheit or pressure measured in pounds per square inch psi exceed safe levels. From the chart we can see that a 3 4 valve set at 40 psi the required system pressure will flow 13 gpm at 10 psi overpressure the set pressure of 40 minus the pressure output of the pump of 50 psi.

Take the old valve to the hardware store and buy a replacement valve that matches it. Be constructed of those materials listed in section p2905 5 or materials tested rated and approved for such use in accordance with asme a112 4 1. Not have a threaded connection at the end of the piping. The valve should be connected to a discharge pipe also called a drain line that runs down the length of the water heater tank.

Not have valves or tee fittings. These valves may look identical but they re set to go off at 30 psi. The relief valve on your water heater has a pipe attached. The discharge pipe shall terminate within 6 inches over the floor and not have any threads on the end nor are there to be any valves in it.

The pipe itself needs to be either copper cpvc or galvanized water piping. The first thing to do is to look at the relief valve sizing chart for hayward relief valves. Another factor in determining the pressure rating of the t p relief valve is the code itself. Most residential water heaters have a 3 4 threaded opening for the discharge pipe.