Watts 740-050 1 1 In Iron Boiler Pressure Relief Valve, 50 psi, Expanded Outlets

The 740 relief valve has a 1 inch female NPT inlet and a 1-1/4 inch female NPT outlet. The inlet threads onto a 1 inch male NPT tapping on the boiler. Because the outlet is expanded to 1-1/4 inch, the discharge line you run to the floor drain has to be 1-1/4 inch pipe, not 1 inch. Never reduce the discharge piping below the outlet size.

Pressure only. The 740 is a boiler pressure relief valve, so it opens on system pressure reaching its 50 psi setting and nothing else. On a water heater, code wants a combination temperature and pressure relief valve with a probe that senses tank water temperature. Don't substitute the 740 for a water heater T and P valve. On a closed hot water heating boiler, a pressure-only valve like this is what the boiler tapping is for.

No. A relief valve set at 50 psi must be matched to a vessel whose maximum allowable working pressure is at or above that setting, and the system's normal operating pressure needs to sit well below 50 psi or the valve will weep. The 740-050 lists a maximum working pressure of 38 psi for the system it protects. For higher pressure boilers, order the 740 at a higher setting within its 30 to 75 psi range.

250 degrees F is the ceiling for the 740. That covers standard hot water heating boilers, which run well below it. Note this is a pressure-only relief valve, so it responds to pressure, not to temperature. If you need a device that dumps on temperature as well, you want a T and P valve rather than this one.

The body is iron. That's the right material for a closed hydronic heating loop, which is what this valve is built for. It is not a potable water valve, and it isn't a lead-free product for potable service. Keep it on the boiler side of the system.

No, the 740-050 is not Buy American Act compliant. If you're procuring for a federal facility or any project carrying a BAA or domestic-preference clause, this valve won't satisfy it and you'll need to source a compliant relief valve instead.

The model is 740-050 1, Watts part number 382820. The 740-050 designation carries the 50 psi setting, and the trailing 1 is the 1 inch inlet. If you're matching an existing valve on the boiler, check the tag on the old body for the psi setting before ordering, since the 740 family runs 30 to 75 psi and the settings look identical from across the room.

That's the expanded outlet. Inlet is 1 inch, outlet steps up to 1-1/4 inch so the valve can pass its full 1,899,000 BTU per hour discharge without the outlet choking the flow. Practically, it means your drain line has to start at 1-1/4 inch female NPT and run full size, pitched to drain, terminating within a few inches of the floor. Bushing the outlet down to match the 1 inch inlet defeats the valve.

Maybe, but a weeping relief valve is usually a symptom rather than the fault. A 50 psi valve drips when system pressure climbs toward 50, which normally points to a waterlogged expansion tank or a leaking fill valve. Swapping in a new 740-050 on a system that's still building pressure gets you a new valve that also drips. Check the expansion tank and the pressure reducing valve first, then replace the relief valve.