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Manufacturer Resources
Product Specs
- Application:
- Boiler
- Body Material:
- Iron
- Country Of Origin:
- United States
- Inlet Connection Size:
- 1 IN
- Inlet Connection Type:
- Female Threaded
- Inlet Thread Type:
- NPT
- Maximum Temperature:
- 250°F
- Maximum Working Pressure:
- 38
- Outlet Connection Size:
- 1 1/4 IN
- Outlet Connection Type:
- Female Threaded
- Outlet Thread Type:
- NPT
- Pressure Range:
- 30 to 75 PSI
- Pressure Relief Setting:
- 50 PSI
- Pressure Steam Discharge Capacity:
- 1,899,000 BTU per hour
- Protection Type:
- Pressure
- Series:
- 740
- Test Lever:
- Yes
- Department:
- Plumbing
- Product Group:
- Plumbing
- Product Subgroup:
- Valves
- Product Type:
- Relief Valve
Watts 382820 – Frequently Asked Questions
1) What size threads does the Watts 740 relief valve, model 382820, have on the inlet and outlet?
Inlet is 1 inch female NPT, outlet is 1-1/4 inch female NPT. The outlet is one size larger than the inlet (that's what Watts calls an expanded outlet), so the discharge line you run off it should be 1-1/4 inch pipe and it must not be reduced anywhere along its length.
2) At what pressure does the Watts 382820 boiler relief valve open?
It's factory set at 50 psi and cannot be field adjusted. The 740 series is offered across a 30 to 75 psi range, so if your boiler tag calls for 30 psi or 75 psi you need the matching set pressure version, not this one. The set point has to be at or below the boiler's maximum allowable working pressure.
3) Is this a pressure-only relief valve or does it also relieve on temperature like a T&P valve?
Pressure only. The 740 is a boiler pressure relief valve with no temperature element, so it will not dump on a high-limit failure the way a water heater T&P valve does. Use it on a hot water heating boiler; for a domestic water heater you need a temperature and pressure relief valve instead. Maximum working temperature is 250 degrees F.
4) Does the Watts 382820 have a test lever for annual testing?
Yes, it comes with a manual test lever. Facility and MRO crews use it for the periodic lift check that keeps the seat from sticking after a long heating season. Lift it only when there is system pressure on the valve, and be sure the discharge line is piped to a safe point first, because the water coming out can be up to 250 degrees F.
5) Can I thread a 1-1/4 inch relief valve straight into my boiler tapping if the tapping is 1 inch?
Yes. The 382820's inlet is the 1 inch end, female NPT, so it threads onto a 1 inch male nipple out of the boiler tapping. The 1-1/4 inch female NPT connection is the outlet side for the discharge piping. Mount the valve upright in the vertical position on the boiler, with no shutoff valve between the boiler and the relief valve.
6) What is the body of the Watts 740 series relief valve made of?
Cast iron body, made in the United States. Iron is the standard body material for closed-loop hydronic boiler service where the valve sees treated system water rather than potable water. For domestic water duty you'd be looking at a bronze-bodied relief valve instead.
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Does the Watts 382820 come with a warranty?
Absolutely. The Watts 382820 is backed by a manufacturer’s warranty.
For full warranty terms, check the product documentation or Contact Us.
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