Boiler displays 24, pressure gauge may be high, water discharged from PRV

Safety first: Allow the system to cool. Hot water discharge can cause burns.

• Check pressure gauge: If pressure rises above 3 bar when hot and PRV discharges, the expansion vessel may be faulty.
• Reduce pressure: Bleed a radiator or use a drain point to lower pressure to about 1.0–1.2 bar when cold.
• Check filling loop: Ensure both filling loop valves are fully closed and the flexible hose is removed if the design allows.
• Engineer tasks:
  • Check and recharge the expansion vessel to the correct pre-charge (typically around 0.8–1.0 bar) using a pump and gauge.
  • Inspect the vessel diaphragm for failure and replace if necessary.
  • Verify the expansion pipework is not blocked.

Persistent pressure rise indicates the expansion vessel or filling loop needs professional attention.