The Watts M375M1-075 3/4 is a 3/4" pressure relief valve for hot water boiler service, factory set at 75 psi. It features a brass body. Rated to 75 psi and up to 250°F.
This boiler pressure relief valve is used in hot water heating and domestic supply boiler applications to protect against excessive pressures on all types of hot water heating supply boiler equipment. It consists of a brass body construction with NPT threaded male inlet and NPT threaded female outlet connections, non-metallic disc-to-metal seating, stainless steel spring, and test lever. It resists corrosive water conditions, sticking and freezing, and prevents water and sediment from being trapped in the seat. It is designed for emergency safety relief, not as an operating control. The standard pressure setting is 75 psi (517 kPa) and is rated to 738,000 BTU/hr.
Features
- Spring loaded
- Soft seated
- Brass body
- Automatic reseating
Common Questions
- What pressure is this valve set to?
- It is factory set to relieve at 75 psi. The setting is fixed and is not field-adjustable.
- Will it fit my water heater — what BTU input does it cover?
- This valve is rated for 738,000 BTU/hr on the ASME pressure-steam basis. Code requires the relief valve's discharge capacity to equal or exceed the input of the appliance it protects, so the number on your heater or boiler nameplate must be at or below that figure. This is the ASME pressure-steam rating quoted at this valve's set pressure; do not compare it against a CSA temperature-steam figure, which is a different measurement entirely.
- Is this ASME rated?
- Yes. It is ASME rated and carries the "HV" code symbol under ASME BPVC Section XIII (the section that replaced Section IV for overpressure protection), and it is National Board (NBBI) certified. Inspectors look for that stamp on the valve body, and it is there.
- Can I use this on potable water?
- No. This is a boiler valve and is not approved for potable water, and that is true regardless of what the lead-free column says — hydronic boiler water is a closed, treated loop and is not drinking water. For a potable hot water heater or storage tank, use a T&P relief valve listed to ANSI Z21.22 / CSA 4.4 instead.
- Does the discharge have to be piped?
- Yes. Codes require the outlet to be piped full-size to a safe point of discharge, terminating with an air gap and no valve, cap, or reducer anywhere in the line — a relief valve that cannot discharge freely is not protecting anything. The manual test lever should be operated at least annually to confirm the valve is not seized.
Specifications
-
Type: Relief
-
Size: 3/4"
-
Inlet Size: 3/4"
-
Outlet Size: 3/4"
-
Connection: NPT
-
Body Material: Brass
-
Max Pressure (psi): 75
-
Pack Quantity: 25
-
Country of Origin: United States
-
Warranty: 1 Year Limited
-
MPN: M375M1-075 3/4
-
Temperature: up to 250°F
-
Certifications: ASME Section XIII (HV), NBBI
-
Lead-Free: No
-
Relief Type: Pressure Only
-
Factory Set Pressure (psi): 75
-
Discharge Capacity (BTU/hr): 738000
-
BTU Rating Basis: ASME Pressure Steam
-
ASME Code Rating: ASME Section XIII (HV)
-
Application: Hot Water Boiler
-
Connection Configuration: MNPT inlet x FNPT outlet
-
Automatic Reseating: Yes
-
Manual Test Lever: Yes
-
Approved for Potable Water: No
-
SentryPlus Alert Flood Sensor: No
