05/10/2026
Reading Your Boiler Pressure Gauge
Is your boiler pressure gauge sitting in the "Red Zone"? Here is what to look for.
Low boiler pressure is the #1 reason boilers suddenly shut off and show a fault code during cold spells—and
in many cases, you can top it up yourself in 60 seconds!
The Quick Pressure Guide:
• Ideal Cold Pressure: Between 1.0 bar and 1.5 bar when the heating is completely OFF.
• Operating Pressure: It's normal for the needle to rise slightly (up to ~2.0 bar) when the radiators are
hot.
• Under 1.0 Bar: Your system is low on water. Use your filling loop under the boiler to slowly top it back up
to 1.2 bar.
Local Tip: If you find yourself topping up the pressure every few weeks, you likely have a small hidden
leak or an issue with your expansion vessel. Continuous fresh water top-ups introduce fresh oxygen, leading
to internal radiator rusting!
Got questions about your pressure loop? Drop a comment below or send a photo of your gauge!
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Website: www.gasplumbing.co.uk
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A local family run business based in Romiley
Service, install and repair gas appliances