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HVAC

How to Check and Repressurise a Boiler

Quick Answer

Check the pressure gauge (should be between 1 and 1.5 bar), open the filling loop valves until pressure rises, then close them.

How to troubleshoot How to Check and Repressurise a Boiler

Low boiler pressure can cause your heating to fail. This guide covers checking the pressure gauge and using the filling loop to repressurise.

Step-by-Step Fix

  1. Locate the pressure gauge on the boiler front panel – it shows the current water pressure.
  2. The ideal pressure is between 1 and 1.5 bar when the system is cold.
  3. If pressure is below 1 bar, locate the filling loop – a silver flexible hose with two valves.
  4. Open both valves slowly and watch the gauge rise to 1.5 bar.
  5. Close both valves firmly and check for any leaks.
  6. Bleed any radiators if needed, then re-check and repressurise again if necessary.

Common Error Codes

CodeMeaningResolution
Pressure drops quicklyLeak in the systemCheck radiators and pipes for visible leaks; call a technician if needed.
Pressure too highOverfilledBleed a radiator to release pressure and water.

Frequently Asked Questions

How often should I check boiler pressure?

Monthly, or whenever the heating system shows signs of inefficiency.

Can I repressurise the boiler while it is running?

It is best to do it when the boiler is off and the system is cold.