When your boiler keeps losing pressure, it can be more than just an annoyance - it often signals underlying issues that need attention. Let's dive into why this happens and what you can do about it.
Your boiler needs the right pressure to function properly - typically between 1 and 2 bar. You can check your boiler's pressure by looking at the pressure gauge, usually visible on the front of your boiler. If it's consistently dropping below 1 bar, something isn't right.
Causes of Low Boiler Pressure
Leaks in Your Heating System
The most common culprit behind pressure loss is a leak somewhere in your heating system. These leaks might be obvious - like a dripping radiator valve or damp patches around pipes. However, they can also be hidden beneath floorboards or behind walls, making them trickier to spot. Even a small leak can cause your system to lose pressure over time.
How to fix leaks
When you can see the leak, first turn off your heating system and let it cool. For radiator valve leaks, try tightening the valve nut slightly with an adjustable spanner. If the leak persists, you'll need to drain that radiator and replace the valve. For pipe joint leaks, sometimes tightening the fitting solves the problem. However, if the joint is corroded or damaged, it needs replacement.
Finding concealed leaks requires professional expertise. Our engineers use specialised leak detection equipment to locate problems without unnecessary damage to your property. We can identify leaks through floorboards and behind walls, and then access them with minimal disruption to your home.
Pressure Relief Valve
Your boiler's pressure relief valve acts as a safety mechanism, releasing excess pressure when needed. Sometimes this valve can become faulty, releasing pressure when it shouldn't. You might notice water dripping from the external overflow pipe - a sure sign your pressure relief valve needs attention.
How to fix pressure relief valves
If your pressure relief valve (PRV) is releasing water when it shouldn't, don't ignore it. First, check if your boiler pressure is too high - anything above 2.5 bar indicates the valve might be working correctly. If pressure is normal but the valve still leaks, it needs professional attention. The valve might need cleaning, adjusting, or replacing. This is not a DIY job - incorrect installation can be dangerous.
After Bleeding Radiators
Have you recently bled your radiators? This common maintenance task often leads to temporary pressure loss. While this is normal, your boiler shouldn't continue losing pressure afterwards.
After bleeding radiators, follow these steps:
Check your boiler pressure gauge - it will likely show below 1 bar
- Locate your filling loop (usually a silver flexible pipe)
- Ensure both ends are properly connected
- Slowly open both valves until pressure reaches 1.5 bar
- Close the valves fully
- Restart your boiler
If pressure drops again within days, you likely have another issue that needs investigation.
Expansion Vessel Issues
Inside your boiler, the expansion vessel manages pressure changes as the water heats up and cools down. If this vessel fails or loses its air charge, your system will struggle to maintain consistent pressure.
How to fix expansion vessel issues
The expansion vessel needs professional attention to either:
- Recharge the air pressure (if the vessel is intact)
- Replace the vessel (if the diaphragm has failed)
We test the vessel's pressure using specialised equipment and can often recharge it during a standard service visit. If replacement is needed, we'll ensure the new vessel is correctly sized for your system.
Need Help?
If you're experiencing pressure problems with your boiler, don't wait until it stops working entirely. Our Gas Safe registered engineers in Medway, Dartford and Gravesend can diagnose and fix issues quickly and safely. Contact us on 07712 172171 and we'll be happy to help.
