Why Your Boiler Keeps Losing Pressure (And When to Call a Plumber in Chislehurst)
- Jamie Cross
- Feb 21
- 2 min read
One of the most common problems homeowners contact us about is a boiler that keeps losing pressure. If you are repeatedly topping up your boiler in Chislehurst, Sidcup or Bromley, it is not normal and usually means a fault somewhere in the heating system.
Your boiler should maintain pressure between 1 and 1.5 bar when cold. If it keeps dropping below this, the system is losing water somewhere.
What Causes Boiler Pressure Loss?
There are several common reasons a boiler keeps losing pressure.
1. A Water Leak in the System
The most common cause is a hidden leak. This may be under floors, inside walls or around pipe joints. Even a very small leak will slowly reduce system pressure over time.
Signs include:
• Damp patches
• Staining on ceilings
• Water near radiators
• Pipes making gurgling noises
Many homeowners don’t notice the leak because it evaporates before becoming visible.
2. Faulty Pressure Relief Valve
Your boiler has a safety valve that releases water if pressure becomes too high. If this valve becomes faulty, it may constantly release small amounts of water outside the property. This is a frequent issue we see in Chislehurst properties.
You might notice a dripping pipe outside your home.
3. Expansion Vessel Problems
Inside your boiler is an expansion vessel that manages pressure changes as water heats up. If this fails, the pressure rises when heating is on and drops again when it cools.
Typical signs:
• Pressure rises when heating is on
• Boiler shuts off
• Pressure drops overnight
4. Recently Bled Radiators
If you have recently bled radiators, pressure will drop slightly. However, if it keeps dropping repeatedly, the problem lies elsewhere.
Is It Safe to Keep Repressurising a boiler that keeps losing pressure?
Many homeowners keep topping up the boiler every few days. This is not recommended.
Constantly adding fresh water introduces oxygen into the system which causes:
• internal corrosion
• radiator sludge
• boiler damage
Eventually this can lead to a full boiler breakdown.
When to Call a Heating Engineer
You should contact a professional if:
• You repressurise more than once a month
• The pressure drops to zero
• The boiler stops working
• You see leaks or damp
We provide boiler repair and heating diagnostics in Chislehurst and nearby areas and can identify the cause quickly.
Can This Be Fixed Easily?
In many cases yes. Common fixes include:
• repairing small pipe leaks
• replacing faulty valves
• recharging expansion vessels
Early diagnosis prevents expensive repairs later.
Local Help in Chislehurst
If your boiler keeps losing pressure, it is almost always a sign of a developing problem. Ignoring it can lead to no heating or hot water when you need it most, especially in winter.
If you are in Chislehurst, Bickley, Mottingham or Sidcup and experiencing this issue, we can inspect the system and restore safe operation.
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