The Watts 740 035 FS 1 1/2 is a 2" pressure relief valve for hot water boiler service, factory set at 35 psi. It features a cast iron body. Rated to 150 psi and up to 250°F.
This pressure relief valve has a 1 1/2 inch NPTF female inlet, 1 1/4 inch NPTF female outlet, and pressure relief setpoint of 35 psi. The valve can be used for hot water space heating boiler applications to protect against excessive pressure. It features an iron body, non-metallic disc-to-metal seating, and test lever. Includes a nonrestrictive discharge drain line flood sensor with SentryPlus Alert® technology to detect excessive water discharges from the relief valve. When paired with an add on connection kit, the sensor is activated to relay alerts for potential flooding events. Connection kit options include BMS, cellular communication, and the Sensor Control Monitor which enables integration with BAS via RS‑485 Modbus or the Nexa platform through Wi-Fi.
Features
- Features a flood sensor with SentryPlus Alert technology to detect excessive water discharges from the relief valve
- Requires purchase of activation kit to activate sensor
- Integrates with the Sensor Control Monitor to deliver maintenance alerts to BAS via RS-485 Modbus or the Nexa platform by Wi-Fi connectivity
- Iron body with forged bronze inlet
- Expanded outlets for hot water space heating boilers
- non-metallic disc-to-metal seating
- Set pressure 35 psi
- Includes: Flood Sensor
Common Questions
- What pressure is this valve set to?
- It is factory set to relieve at 35 psi. The setting is fixed and is not field-adjustable. Note the 150 psi figure in the specifications is the maximum of the series' pressure range — the ceiling the body is built for, not this valve's relief point. This valve opens at 35 psi. Match it to the appliance nameplate: the relief setting must not exceed the working pressure stamped on the vessel you are protecting.
- 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
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Type: Relief
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Size: 2"
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Inlet Size: 1-1/2"
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Outlet Size: 2"
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Body Material: Cast Iron
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Max Pressure (psi): 150
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Pack Quantity: 6
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Country of Origin: United States
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Warranty: 1 Year Limited
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MPN: 740 035 FS 1 1/2
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Temperature: up to 250°F
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Certifications: ASME Section XIII (HV), NBBI
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Lead-Free: No
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Relief Type: Pressure Only
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Factory Set Pressure (psi): 35
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ASME Code Rating: ASME Section XIII (HV)
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Application: Hot Water Boiler
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Connection Configuration: FNPT inlet x FNPT outlet
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Manual Test Lever: Yes
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Approved for Potable Water: No
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SentryPlus Alert Flood Sensor: Yes
