Install and test the CH and DHW relief valves

What is going on

Relief valve rules for the central heating loop and the DHW loop on combi models.

Check in this order

1. Use the supplied 30 psi CH relief valve at the top of the boiler. Do not use a valve rated above 50 psi.
2. Field-supply a DHW relief valve rated to ANSI Z21.22 / CSA 4.4, not above 150 psi.
3. Install no valve between the relief valve and the boiler, and no valve in the discharge line.
4. Run the discharge line plain (unthreaded) and pitched down, ending at least 6 in. above a floor drain where the discharge is visible. Keep it short and the same size as the valve outlet.
5. Use a discharge material rated for 375°F or higher. Do not route it where it can freeze.
6. After filling and pressurizing, lift the lever to test that the valve discharges freely. Replace any valve that does not.
7. Have relief valves inspected at least every three years and replaced as needed by a licensed plumber or qualified tech.

More general guides

• Combustion air and leak protection checks during install
• Expansion tank and air elimination
• Low water cut-off wiring (field supplied)
• Primary/secondary piping and 3-way valve for heating-only use
• Removing the boiler from a common vent system
• Wall mounting the boiler