Watts 174A-050 3/4 3/4 In Bronze Boiler Pressure Relief Valve, 50 psi, Threaded Female Connections

Yes, if that tapping is 3/4 inch NPT female. The 174A-050 has 3/4 inch female NPT on both the inlet and the outlet, so it threads onto a 3/4 inch male nipple off the boiler tapping, and the discharge side takes 3/4 inch male pipe for the drop to the floor. Both ends are the same size, so no bushing is needed on a straight 3/4 inch run.

It is factory set to relieve at 50 psi. That setting is fixed on this model, it is how the -050 suffix is designated. The 174A series covers settings from 30 to 150 psi, so if your boiler's MAWP calls for a different relief point you order the 174A at that setting rather than trying to change this one.

Match the relief setting to the boiler, not the piping. A 50 psi valve is for a boiler whose maximum allowable working pressure is 50 psi or higher, which covers most residential and light commercial hydronic boilers rated at 50 psi. If your boiler tag reads 30 psi MAWP, this valve is too high and it will not protect the vessel, you want the 30 psi version of the 174A instead. The series is built across 30 to 150 psi for exactly that reason.

No. This is a pressure-only relief valve for a hot water heating boiler, not a T and P valve. It senses pressure alone with no temperature element, and it is not lead free, so it does not belong on potable water. For a domestic water heater you need a temperature and pressure relief valve with a lead free body.

The valve itself is all you get, so plan on a 3/4 inch male nipple into the boiler tapping and 3/4 inch pipe for the discharge line. That discharge has to be full size the whole way, no reduction and no valve in it, terminated near the floor so a discharge cannot scald anyone. Pipe dope or tape on the male threads, and mount the valve vertical with the test lever up.

250 degrees F maximum. That is above the boiling point at the pressures a hydronic system runs, so it covers normal hot water heating service comfortably. The body is bronze, which is what gives it that rating and holds up in boiler water service better than a plated or die cast body.