How to Repressurise Your Heating System

If the pressure gauge on your HeatCore C1 drops below 1.0 bar, the boiler may not fire for heating. Repressurising is a simple task that takes a few minutes using the filling loop beneath the boiler.

What you'll need

Access to the filling loop — a braided flexible hose located directly below the boiler, connecting the mains cold water supply to the heating circuit
No tools are required

Steps

Switch the boiler off. Press the power button on the display or turn the boiler off at the isolation switch. Allow the system to settle for a minute.
Locate the filling loop. Look beneath the boiler for the braided metal hose. At each end of the hose you will find a small valve — these are usually lever-type handles or square-head taps.
Open the first valve. Turn it a quarter turn so the handle lines up with the direction of the hose. You will not hear anything at this stage — this valve simply opens the path between the mains and the filling loop.
Slowly open the second valve. Turn it gradually. You will hear water begin to flow into the heating system. Open it slowly and steadily — filling too fast can push air into the system.
Watch the pressure gauge. Monitor the gauge on the boiler display (or the analogue gauge if fitted). The needle will begin to rise as water enters the system.
When the gauge reaches 1.0–1.5 bar (the green zone), close the second valve first, then close the first valve. Both handles should be perpendicular to the hose when fully closed. Do not leave either valve open.
Switch the boiler back on. The boiler will resume normal operation. The display should no longer show a low pressure warning.
If air has entered the system, bleed the nearest radiator. If you hear gurgling from radiators after repressurising, bleed the radiator closest to the boiler to release any trapped air. See our guide: How to Bleed Your Radiators.

Important: NEVER fill the system above 2.5 bar. Overpressurising will cause the pressure relief valve to discharge water through the external overflow pipe. If the pressure gauge will not hold between 1.0 and 1.5 bar after filling — or if you are repressurising more than once a month — there is likely a leak in the system. Call a heating engineer to investigate.

Tip

After repressurising, check the pressure again the following day when the system is cold. If it has dropped noticeably (more than 0.3 bar), inspect visible pipework, radiator valves, and the area beneath the boiler for any signs of a leak. A slow, persistent drop always indicates water leaving the system somewhere.