Watts 3L-100 3/4 Relief Valve, Brass, NPT

The Watts 3L-100 3/4 is a 3/4" pressure relief valve for tankless / thermal expansion service, factory set at 100 psi. It features a brass body. Rated to 150 psi.

This 3/4 inch pressure relief valve is used in residential applications to protect against excessive pressure on domestic storage tanks and tankless water heaters. It consists of a brass body construction with NPT threaded male inlet and NPT threaded female (drain) outlet, test lever, and stainless steel spring. It is ANSI Z21.22 approved, ASME rated and design certified and listed by CSA. The pressure relief is set at 100 psi (6.9 bar).

Features

• Brass body construction
• Pressure relief is set at 100 psi (6.9 bar)
• Test lever included
• ASME rated and CSA certified

Common Questions

What pressure is this valve set to?

It is factory set to relieve at 100 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 100 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. 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.

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): 150
• Pack Quantity: 50
• Country of Origin: United States
• Warranty: 1 Year Limited
• MPN: 3L-100 3/4
• Certifications: ASME Section XIII (HV), ANSI Z21.22, CSA 4.4
• Lead-Free: No
• Relief Type: Pressure Only
• Factory Set Pressure (psi): 100
• ASME Code Rating: ASME Section XIII (HV)
• Application: Tankless / Thermal Expansion
• Shank Length: Standard
• Connection Configuration: MNPT inlet x FNPT outlet
• Manual Test Lever: Yes
• Approved for Potable Water: No
• SentryPlus Alert Flood Sensor: No