Watts LF40XL-150210 3/4 3/4 IN Lead Free Brass Automatic Reseating T and P Relief Valve, 150 psi, 210 degree F, Test Lever, 5 IN Extension Thermostat

Yes, if the tapping is 3/4 inch NPT. The LF40XL-150210 has a 3/4 inch male NPT inlet that threads into the heater tapping and a 3/4 inch female NPT outlet for the discharge tube. Both ends are 3/4 inch, so no bushing is needed on a standard residential or light commercial heater.

The copper probe on this Watts T and P valve extends 5 inches into the tank, so the tapping has to have at least that much clear space inside. The long probe is meant for heaters and storage tanks where the sensing element needs to reach past the insulation and tank wall into the water. On a small tank, a compartment heater, or a side tapping with obstructions close behind it, a short-shank T and P valve is the right call instead.

It relieves at 150 psi or 210 degrees F, whichever condition hits first. That is a temperature and pressure valve, not pressure-only, so it protects against both a runaway thermostat and overpressure. Confirm the 150 psi setting is at or below the working pressure rating stamped on your water heater before installing it.

Size it off the two discharge ratings. The LF40XL-150210 3/4 handles 1,437,600 BTU per hour on pressure discharge and 205,000 BTU per hour on temperature discharge. The temperature figure is the limiting one on a water heater, so the heater's input rating must not exceed 205,000 BTU per hour. Above that, you need a larger T and P valve.

Yes. The body is lead free bronze and the valve is flagged lead free, so it is intended for potable hot water service on domestic water heaters and storage tanks.

It is an automatic reseating valve, so it closes again once temperature and pressure drop back below the 150 psi / 210 degree F settings. The test lever lets a maintenance tech exercise the valve on a routine check without shutting the heater down.

Maximum working pressure is 113 psi, with the relief point set at 150 psi. Normal line pressure sitting close to the relief setting causes weeping, so if your building static pressure is running high you want a pressure reducing valve upstream rather than a different T and P.

The valve is Watts model LF40XL-150210 3/4, Watts part number 556016, in the LF40L series. That is the identifier to match if you are standardizing T and P valves across a portfolio of heaters.

It is flagged Buy American Act compliant with USA origin, which is what a federal, school district, or municipal spec typically asks for on plumbing trim.