A properly functioning boiler should maintain pressure between 1 and 2 bar. If you've noticed your boiler's pressure gauge dropping below this range, you're not alone - it's one of the most common boiler issues we encounter. Let's explore why this happens and what you can do about it.
Common Causes of Low Boiler Pressure
1. Leaks in the Boiler or System
Leaks are a primary cause of pressure loss. These can occur in various places:
- Within the boiler itself
- Around radiator valves
- Along pipework
- At pipe joints and connections
Look for signs such as damp patches, rust spots, or water droplets. Even small leaks can cause significant pressure drops over time.
2. Faulty Pressure Relief Valve (PRV)
The PRV is designed to release excess pressure from your system. When faulty, it may release pressure unnecessarily. Check your external overflow pipe - if you notice water dripping, your PRV might be the culprit.
3. Damaged Expansion Vessel
This component accommodates water expansion as it heats. A damaged or improperly charged expansion vessel can't maintain proper system pressure. Watch out for:
- Frequent pressure drops
- Strange noises from the boiler
- Inconsistent pressure readings
4. Recently Bled Radiators
After bleeding radiators, some pressure loss is normal. However, significant drops might indicate a larger issue. Always check your pressure gauge after bleeding radiators.
5. Broken Boiler Parts
Several components can cause pressure issues if they fail:
- Automatic air vents
- Washers and seals
- Ring joints
- Heat exchangers
6. Corrosion or Lose Connections
Over time, your system may develop:
- Corroded pipes and radiators
- Loose pipe connections
- Deteriorating seals These issues typically cause gradual pressure loss.
How to Fix Low Boiler Pressure
Repressurising Your Boiler
If your pressure is low, follow these steps:
- Switch off your boiler and let it cool completely
- Locate the filling loop (usually a flexible silver hose with two valves)
- Ensure the filling loop is securely attached
- Slowly open both valves to allow cold mains water in
- Watch the pressure gauge carefully
- When it reaches 1.5 bar, close both valves tightly
- Switch the boiler back on and check it's working properly
When to Call a Professional
Contact a Gas Safe registered engineer if:
- You notice frequent pressure drops
- There are visible leaks you can't easily fix
- Do you suspect internal boiler component issues
- Your boiler shows other signs of malfunction
- You're not confident about repressurising yourself
Remember that boilers are complex systems that can be dangerous if mishandled. Never attempt repairs beyond your competence level - it could be dangerous and might void your warranty.
Need Help?
If you are facing any issues with your boiler, including pressure loss, our Gas Safe registered engineers are here to help. Contact us today on 07402806032 and speak with our heating engineers in Acton, Hanwell and Ealing.
