The Watts 40L-3 125/210 FS 3/4 is a 3/4" temperature and pressure (T&P) relief valve for commercial water heater service, factory set at 125 psi and 210°F. It features a bronze body. Rated to 150 psi and up to 210°F.
This automatic reseating temperature and pressure relief valve has a 3/4 inch NPTF male inlet, 3/4 inch NPTF female outlet, 3 inch coated thermostat, pressure relief setpoint of 125 psi, and temperature relief setpoint of 210 degrees F. The valve can be installed directly in tank tappings for commercial applications to provide protection for hot water supply tanks and hot water heaters. It features a bronze body, tamper resistant bonnet screws, 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
- Bronze body
- Tamper resistant bonnet screws
- 3 Inch coated thermostat length
- Non-mechanical seat to disc alignment
- Set pressure 125 psi
- Includes: Flood Sensor
- Includes: Tamper Switch
Common Questions
- What pressure is this valve set to?
- It is factory set to relieve at 125 psi and 210°F. 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 125 psi. Match it to the appliance nameplate: the relief setting must not exceed the working pressure stamped on the vessel you are protecting.
- Will it fit my water heater — what BTU input does it cover?
- Sizing a T&P valve is a capacity question, not just a thread question: the valve's BTU/hr discharge rating must equal or exceed the input on the heater's data plate. Watts does not publish a capacity for this specific model in the data we carry, so check the BTU/hr figure on the valve's spec sheet against your heater's nameplate input before ordering. The 3" thermostat probe also has to reach the hot water in the tank — confirm it suits your tapping.
- 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. It is also ANSI Z21.22 / CSA 4.4 approved, which is the listing water heater relief valves are required to carry. Inspectors look for that stamp on the valve body, and it is there.
- Can I use this on potable water?
- No. This model is not certified lead-free, so it cannot be installed in a potable (drinking) water line under the NSF/ANSI 372 weighted-average lead rule. Use it on non-potable service, or order the "LF" version of this model for potable water.
- What thermostat length do I need?
- This valve has a 3" thermostat probe. The probe must reach into the top 6" of the tank's stored water to sense temperature, so it has to match the depth of your tapping — too short and the valve never sees the overheat it exists to catch. Watts builds this series in several probe lengths; measure before ordering.
- 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: 3/4"
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Inlet Size: 3/4"
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Outlet Size: 3/4"
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Body Material: Bronze
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Max Pressure (psi): 150
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Pack Quantity: 12
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Country of Origin: United States
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Warranty: 1 Year Limited
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MPN: 40L-3 125/210 FS 3/4
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Temperature: up to 210°F
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Certifications: ASME Section XIII (HV), NBBI, ANSI Z21.22, CSA 4.4
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Lead-Free: No
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Relief Type: Temperature & Pressure
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Factory Set Pressure (psi): 125
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Temperature Setting (°F): 210
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ASME Code Rating: ASME Section XIII (HV)
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Application: Commercial Water Heater
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Thermostat / Element Length (in.): 3
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Shank Length: Standard
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Connection Configuration: MNPT inlet x FNPT outlet
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Automatic Reseating: Yes
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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
