Boiler leaking from pressure relief valve discharge pipe

Safety first: Allow the system to cool. The relief valve may discharge very hot water or steam.

• Step 1 – Check system pressure: Read the pressure gauge when the system is cold. If above the recommended value (often 12–15 psi), drain some water from a drain valve until pressure is correct.
• Step 2 – Test expansion tank: Locate the expansion tank near the boiler. With the system depressurized, measure the air charge at the Schrader valve using a tire gauge. It should match the boiler’s cold fill pressure. If water comes out or pressure is zero, the tank has failed and must be replaced.
• Step 3 – Inspect relief valve: If pressure is normal and the expansion tank is good but the valve continues to drip, the relief valve seat may be fouled. Gently lift and release the test lever to flush debris, then monitor. If dripping persists, replace the relief valve.
• Step 4 – Check for overheating: Ensure the circulation pump is operating and all valves are open. Overheating can cause pressure spikes.

Warning: Never cap or plug the relief valve discharge. This is a critical safety device.