Watts 0121321 1/2 IN Lead Free Self Closing Temperature and Pressure Relief Valve, 150 psi, 210 degree F, Test Lever, Short Thermostat

No. The LF1L 0121321 has a 1/2 inch male NPT inlet, so it only threads into a 1/2 inch T&P tapping. Most residential and light commercial water heaters use a 3/4 inch tapping, and you should not bush a 1/2 inch relief valve into a larger opening on a heater sized for 3/4 inch relief. Check the tapping size on the tank before ordering this one.

The LF1L 0121321 has a 7/8 inch shank, which is the short thermostat version. It's intended for tanks where the tapping puts the probe into the water at that depth. If your heater has thick insulation or a deep boss and calls for an extended shank, a 7/8 inch thermostat may sit in the jacket instead of the water and won't sense tank temperature correctly.

It's factory set to relieve at 150 psi and at 210 degrees F. The 150 psi setting has to be at or below the working pressure rating stamped on your water heater, so match the valve setting to the tank rating rather than to your street pressure.

The outlet is 1/2 inch female NPT, so the drop leg threads directly into the valve with a 1/2 inch male fitting. Run it full size the whole way, no reducing, and terminate it so it discharges downward to within a few inches of the floor or to an approved drain with no valve in the line.

The LF1L 0121321 has a 15,000 BTU per hour temperature steam discharge capacity. That has to equal or exceed the input rating of the heater it protects, so it suits small point of use and light duty tanks. A 40,000 BTU residential gas heater needs a valve with a much higher rated capacity, not this one.

The body is a lead free copper silicon alloy, so it's built for potable domestic hot water service. It's made in the United States.

It's a self closing temperature and pressure relief valve, so it reseats once pressure and temperature drop back below the setpoints. It also has a manual test lever for the periodic pull test. If it keeps weeping after reseating, the seat is fouled and the valve gets replaced, not repaired.

No. The 0121321 is a combination temperature and pressure device and always carries the 210 degree F thermostat probe. If the application only calls for overpressure protection, such as a thermal expansion point on a cold line, a straight pressure relief valve is the correct part.