Boiler Pressure Explained: How to Check and Set Your Boiler Pressure
A healthy boiler keeps your home warm and your hot water flowing. One of the most common reasons for boiler breakdowns is incorrect pressure - but understanding and adjusting it is easier than you might think. In this guide, Trusted Boilers Ltd. explains what boiler pressure is, why it matters, and how you can safely check and set it in your own home.
What Is Boiler Pressure?
Boiler pressure is the force of water circulating through your central heating system, measured in 'bar' on your boiler’s pressure gauge. The right pressure ensures your radiators heat up properly and your boiler runs efficiently.
Ideal boiler pressure (when cold):
- Usually between 1.0 and 1.5 bar
- Check your boiler manual or the sticker near the gauge for the exact range
Why Is Correct Boiler Pressure Important?
- Too low: Heating may not work, boiler could overheat, lock out, or show a fault code
- Too high: System could leak, pressure relief valve may discharge water, or boiler may shut down
How to Check Your Boiler Pressure
- Locate the pressure gauge (usually on the front of your boiler)
- Read the needle:
- In the green zone (1.0–1.5 bar, cold) – all good!
- Below 1.0 bar – pressure too low
- Above 2.0 bar (cold) – pressure too high
How to Top Up (Increase) Boiler Pressure
If your pressure is too low:
- Turn off the boiler and let it cool
- Find the filling loop (a silver/grey flexible hose with taps/valves at both ends)
- Open both valves slowly – you should hear water entering the system
- Watch the gauge – when it reaches 1.2–1.5 bar, close both valves
- Turn the boiler back on and reset if needed
Tip: Only top up a little at a time—overfilling can cause pressure to go too high.
How to Release (Reduce) Boiler Pressure
If your pressure is too high:
- Bleed a radiator: Use a radiator key to release a little water (have a towel ready)
- Check for leaks: If you have to reduce pressure often, call an engineer
When to Call a Professional
- If your pressure drops repeatedly
- Water leaks from the boiler or radiators
- You see fault codes or the boiler shuts down
- You’re not confident adjusting the pressure yourself
Regular Servicing Prevents Pressure Problems
Serving South London & North Surrey
Trusted Boilers Ltd. provides expert advice, repairs, and servicing across Wimbledon, Sutton, Banstead, Epsom, Croydon, and surrounding areas.
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