How to Identify and Fix Central Heating Leaks: A Step-by-Step Guide for Homeowners.

"Efficient central heating system with radiator

Central heating leaks can spell trouble, potentially leading to breakdowns. Recognizing signs like pressure loss or hissing noises is crucial, especially during the winter months when usage is high, and frost damage is a risk. Identifying and addressing these leaks promptly can save on repair costs. While we recommend a professional Gas Safe engineer for inspections, you can follow these steps if you feel confident.

1. Visual Inspection Around the Boiler:

Visible water damage around a boiler

  • Look for leakage or indicative signs of moisture damage around the boiler.
  • Do not check warm piping and fittings.
  • If there are puddles or even visible leaks, make sure to have someone come in and correct the problem before more damages arise as a result.

2. Use of Colored Paper:

wet colored paper for leak detection

  • Place colored paper under the boiler to detect water drops.

  • Follow the path of drops to pinpoint the leak source.

3. Check Radiator Valves:

  • Inspect radiator valves for potential defects that could result in leaks.
  • Tying some tissue around the piping could make it easier to notice a leak, as you come back after about an hour. …any moisture spots on the tissue would indicate a minor leak that needs treatment.
  • Replace valve if necessary.

4. Inspect Thermostatic Radiator Valves (TRVs):

  • Look for wet areas around TRVs and water near the pin as this will indicate a leak again do this by sight or touch around them for any signs of dampness.
  • Address leaks promptly for efficient radiator operation
Close-up of rust on a radiator, indicating a potential leak

5. Inspect radiators for Pinhole Leaks:

  • Rust on radiators may indicate pinhole leaks.
  • Check for leaks with the heating on; use tissue to identify leak locations.


Fixing a Pinhole Leak in a Radiator:

  • Add an internal leak sealer to the system upon locating the pinhole.
  • Follow instructions on the sealant packaging for effective use.
Mould growth on walls, a sign of potential water leaks in the central heating system

6. Check for Wall Damage:

  • Check for wet patches or mould on the walls; small water leaks from pipes may lead to mold and may require inspection. Bear in mind that mould can also signal poor ventilation amongst other things, if you have any doubt it may be a wise idea to consult an expert.

  • Fixing Pipe Leaks Using a Leak Sealer:

    • Locate the leak; consider a professional for pipework issues.
    • For radiator leaks, use a leak sealer designed for radiators.
    • Evaluate if the central heating system needs replacement for long-term efficiency.

  1. How Central Heating Leak Sealers Work:

    • Designed to repair and prevent leaks in pipework.
    • Form a barrier to seal tiny internal micro leaks.
    • A cost-effective option for smaller leaks, but not suitable for all situations.
  2. Adding Leak Sealer to the System:

    • Follow instructions on the specific leak sealer packaging.
    • General steps include emptying the header tank, pouring in the sealer, and ensuring even distribution.
    • If unsure, consult a professional for proper application.
  3. When to Call Professionals:

    • Leak sealers are suitable for small leaks; may impact warranties.
    • Larger leaks may require Gas Safe engineer intervention.
    • If uncertain about the source or fix, seek professional assistance.


Of course, leak sealers are a reasonable solution but larger leaks and systemic problems may necessitate assistance from professionals. If you are undecided about this issue, or do not have the experience and time necessary to handle it on your own today reach out to us today so we can assess how much assistance is required.