Furnace shows high water pressure alarm, safety valve may discharge water

Safety: Hot water under pressure can cause burns. Do not cap or block the safety valve discharge pipe.

• Check pressure reading: Confirm the system pressure on the gauge. If above the recommended maximum (often 2.5–3 bar), action is needed.
• Verify filling loop: Ensure the manual fill valve or filling loop is fully closed and not passing. Replace if it cannot be fully shut.
• Reduce pressure: When the system is cool, bleed water from a radiator or drain point until the pressure returns to the normal cold range.
• Check expansion vessel: Tap the vessel: a waterlogged vessel sounds dull. A technician should isolate, drain, and check the air charge with a gauge; recharge or replace as required.
• Inspect safety valve: If the valve continues to drip at normal pressure, it may be fouled by debris and require replacement.