Boiler pressure rises excessively when heating; the relief valve opens and discharges water.

Safety first: Hot water from the relief valve can cause burns. Keep clear of the discharge pipe.

• Check expansion tank: Locate the diaphragm expansion tank near the Utica boiler. Tap it; it should sound hollow on the top and solid on the bottom. If it feels full of water or is heavy, it may be waterlogged.
• Test tank pressure: With system pressure relieved and isolated, use a tire gauge on the tank's Schrader valve to check the air charge (typically 12 psi). Recharge or replace if no air pressure is present.
• Verify fill pressure: Ensure the system is not overfilled. Drain water until the cold pressure is at the recommended level.
• Check reducing valve: A stuck pressure reducing valve can overfill the system. Replace if it continues to feed water above the set pressure.
• Indirect/combi check: On systems with a domestic hot water coil, an internal leak can raise boiler pressure. This requires professional diagnosis.