Pressure and water
A sealed heating system needs water at a working pressure, shown on the boiler's gauge. These entries cover what the reading means, how makers say to top it up, and when falling pressure needs an engineer.
- Boiler pressure
Boiler pressure is the water pressure in a sealed heating circuit, and the right reading depends on the model, because manuals differ on when to top up and what to fill to.
- Repressurising a boiler
To repressurise a boiler you let mains water in through its filling device, watch the gauge, stop at the figure in your own user manual, then close and disconnect the device.
- Filling loop
A boiler filling loop is the valved connection that lets mains water into a sealed heating circuit to raise its pressure.
- Pressure keeps dropping
Boiler pressure that keeps dropping means water is leaving a sealed system, and makers treat a regular need to top up as a sign of a fault or leak.
- Pressure too high
Boiler pressure too high usually follows over-filling, a filling device letting water through, or a fault, and the safe response depends on the reading and your manual.
- Pressure relief valve
A boiler's pressure relief valve is a safety device that opens to let water out of the system when pressure gets too high, then closes again.