What to Do If Your Boiler Loses Pressure?
What to Do If Your Boiler Loses Pressure: A Homeowner’s Guide
If your boiler’s pressure gauge is showing a low reading — usually below 1 bar — it could stop your heating and hot water from working efficiently. While it’s often a quick fix, recurring pressure loss means there’s an underlying issue that needs professional attention.
What Does Boiler Pressure Mean?
Boiler pressure refers to the water pressure within your heating system. It ensures hot water can circulate through your radiators and pipes. Most boilers operate best between 1 and 1.5 bar when cold. If the pressure drops too low, your boiler might shut off as a safety precaution.
Common Causes of Boiler Pressure Loss
- Bleeding radiators: Air escapes, but water levels drop — reducing pressure.
- Small leaks: Even minor leaks from valves, pipe joints, or radiators can lower pressure over time.
- Faulty pressure relief valve: If it’s leaking, water escapes from the system.
- Expansion vessel failure: When the internal air cushion wears out, pressure fluctuates and falls.
How to Check and Top Up Boiler Pressure
Step 1: Make sure your boiler is switched off and cool.
Step 2: Locate the pressure gauge — typically on the front of your boiler or control panel.
Step 3: Use the filling loop (a small flexible silver hose beneath the boiler) to add water slowly until the gauge reaches 1.2–1.5 bar.
Step 4: Close the valves securely and turn the boiler back on. The pressure should stay steady.
If you’re unsure or the pressure drops again quickly, do not keep refilling — this could mask a leak or cause corrosion. Call an engineer to find the root cause.
When to Call a Professional
- The pressure keeps dropping even after topping up.
- You can hear hissing or dripping inside the boiler casing.
- You spot visible leaks or damp patches near the boiler or pipes.
- The pressure gauge rises above 2.5 bar when hot (a sign of expansion fault).
Our expert team at P A Henery Ltd can diagnose and repair pressure loss safely and efficiently. Learn more about our boiler servicing and maintenance options.
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