How to Re-pressurise Your Boiler — Step-by-Step

What Is Boiler Pressure?

Your boiler maintains a pressurised closed loop of water that circulates through the radiators and back. Normal operating pressure is 1–1.5 bar when cold, rising to around 2 bar when fully heated. If pressure drops below 1 bar, most modern boilers will lock out and display an error code (commonly F22 on Baxi, A1 on Worcester Bosch).

Why Does Pressure Drop?

A small pressure drop after bleeding radiators is normal. Other causes include: a minor system leak (often at a radiator valve), a faulty pressure relief valve, or simply natural pressure loss over time. If pressure drops repeatedly without bleeding, there's likely a leak somewhere in the system — call us for a diagnostic check.

How to Repressurise Your Boiler

Step 1: Turn the boiler off and let it cool completely.

Step 2: Find the filling loop — a flexible grey or silver hose with small valves at each end, usually located under the boiler.

Step 3: Open both valves on the filling loop (turn the handles to align with the hose direction). You'll hear water entering the system.

Step 4: Watch the pressure gauge on the boiler. Stop when it reads 1.0–1.5 bar.

Step 5: Close both valves fully. Remove the filling loop if it's a removable type and store it safely.

Step 6: Switch the boiler back on. The error code should clear. If not, refer to your boiler manual.

What If the Pressure Keeps Dropping?

If you need to re-pressurise more than once a month, you have a leak. This could be as simple as a weeping radiator valve or as complex as a faulty heat exchanger. Don't ignore persistent pressure loss — call us for an inspection before the situation worsens.