GeneralHow-To2026-02-28
How to Repressurize a Boiler (Step by Step)
Low boiler pressure is easy to fix with the filling loop — here's how to do it safely.
If your boiler has locked out on low pressure, repressurizing via the filling loop usually restores it.
Find the filling loop
Locate the filling loop — a flexible braided hose with one or two valves beneath the boiler connecting the cold supply to the system.
Top up to 1–1.5 bar
With the boiler off and cool, open the valve(s) slowly and watch the gauge rise to 1–1.5 bar, then close them firmly and reset the boiler.
Key takeaways
- Top up only when cool
- Aim for 1–1.5 bar
- Close the filling loop fully
- Recurring loss means a leak
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