How To Find and Fix Water Leaks In Central Heating

If you have a leak in your central heating system, it can be difficult to find out where it is.  There are many areas where leaks can occur, some being more common than others, like radiators and pipe joints. In some cases, you can’t see where the leak is coming from.  Here, we look at different ways to find water leaks and fix them. 

Quick ways to find a leak in your central heating system are to check the boiler pressure gauge to see if it has fallen to zero, then go round to each radiator and check for damp or wet flooring around them. You may also notice stains on walls and ceilings near where pipes run.

Find water leaks in a system

Find a central heating system water leak

Where to look for water leaks

Low boiler pressure gauge

image of low boiler pressure on gauge

Checking the pressure gauge on the boiler, if it’s lower than usual, this could be a sign of a leak.

If your boiler is constantly running, it could be a sign of a leak. Cold water continuing to feed the boiler even without a demand for hot water or heating, means a sink tap or pipe may be leaking.

Damp patches on walls and ceilings

If you think you may have a leak coming from ceilings, behind walls, or other hard to see places, the best thing to do is call a professional to come and take a look. They’ll be able to help you locate the source of the leak and fix it, so that your central heating system is back up and running smoothly.

image of damp patch on ceiling due to water leak

Check under radiators and radiator valves

These are common areas of leaks.  Go round the house and check at each end of the radiators.  You may notice the carpet wet underneath the valves.  Place a tray underneath to make sure and wait a day to see if it is that.

Although valves are more prone to leaks than the actual radiator, rust and corrosion inside a radiator can cause it to leak.  You can also spot these by wet carpet stains.  It is best to replace the radiator rather than trying to seal it.

Mould growth on walls and ceilings

If you see any dampness, this could be caused by a leak.  If you’ve got wall stains, mould is a sign of a water leak. Mould loves damp and humid conditions, so if you’ve got wall or ceiling stains, it’s a good idea to check for mould growth.

You can usually tell if it’s mould by the colour and texture of the stain. If the stain is dark and fuzzy, it’s probably mould.

But try not to confuse a leaking central heating system with a leaking roof. A ceiling stain with no pipes running over or near it usually means you need to fix the roof.

Boiler constantly running

If the boiler is constantly running, check for leaks by going around the general area where the boiler is located.

Don’t ignore a boiler that’s constantly running. It could be wasting money and damaging your boiler in the long run. Fixing a small leak now will save you money and help prevent bigger problems down the road.

Leaks coming from inside the boiler

After thoroughly checking around the house, if you find no signs of a leak but still need to top up the pressure, it is likely inside the boiler.  As the leak gets worse, you may need to top up the boiler more often. 

One way to find out is to place a tray or coloured paper under the boiler to catch dripping water.  But if the water leak is going into the condense pipe, you will not be able to spot it this way.  Call an engineer to sort out.

Higher water bills

If you have a leak in your home, one indication is a spike in your water bill. If you notice this, check for other signs of a leak, such as water stains on the ceiling or walls, damp patches, or musty smells. Once you’ve confirmed that there is a leak, turn off the water at the main stop tap and go looking for the general area of the leak.

image of an astonished man seeing a high bill

Quick fix for a leak

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Using leak sealer

If you can’t find a leak anywhere in the house, use leak sealer.  It can work really well to stop small leaks in the central heating system including pipes, joints and radiators.

A leak sealer is a type of liquid that circulates around the central heating system until it finds the source of a leak, whether in the pipes, joints or the radiators. Once it reaches the correct temperature, it melts to form a seal, stopping further leaks. 

It takes less than 24 hours to work and does not cause any blockages within the boiler, so isn’t harmful to boiler components.

Pipe leaks can often be fixed with a simple repair. But if you ignore them, small leaks can turn into big problems that will cost you a lot of money to fix. So if you see peeling paint or wallpaper, or blistering paint, don’t ignore it!

These could be signs of a leak somewhere in your home. Inspect exposed pipes looking for corrosion and moisture around the pipes. If you can’t find the leak yourself, call a plumber. They’ll be able to find and fix the leak.

If you have trouble finding a leak

Hometree offers customers peace of mind with home care packages for their boiler, central heating, plumbing, drains and home electrics all at an affordable monthly or annual cost.

Hometree’s aim is to take the stress out of boiler servicing and home maintenance with unlimited call-outs and a 24/7 helpline, as well as a no price-hike promise.


There are a few other things you can do to check for leaks, such as:

  • Low boiler pressure gauge.
  • Damp patches on walls or ceilings.
  • Check near radiators.
  • Wet carpets.
  • Mould growth.
  • Boiler constantly running.
  • Higher water bills.
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