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How to Fix a Pinhole Leak in a Central Heating Radiator?


A leaking radiator is both problematic and annoying. It will not only reduce the efficiency of your boiler but will also gravely damage your floor or other furnishings due to the colourised water spillage. But what causes leaking in and around your radiators? And how can you find and fix it?

Well, if those are the questions currently baffling you, then you’ve come to the right place. In this guide, we will explore the reasons why your radiator may be leaking and while at it, exhaustively unveil all you need to know about fixing a pinhole leak.

What causes pinhole leaks?

As is the case with most metalwork, interaction with water causes corrosion and rust. Most radiators and their pipework get installed with inhibitor agents that prevent or slow down the rusting process. However, in most cases, rusting is inevitable. If the central heating system is not regularly maintained, rust is a certainty along pipes and particularly the radiators.

Over time, bits of tiny rusty metals break away from the metalwork. They settle at the bottom of the radiators or further along the duct and form a brown sludge. The sludge flakes against the inside of the radiators and eats away bits of the radiators slowly. The problem will eventually create tiny holes in the radiators or the pipes. If these tiny holes are not detected and mended in advance, they would cause leakage.

How to locate a pinhole leak

Locating the tiny hole is pivotal to fixing your radiator or your pipes. The source of the leakage may be the radiators or the pipework, and it will require different tactics to detect pinhole leakages in either of them.

How to locate a pinhole leak in radiators

A wet spot on your floor should alert you to the possibility of a pinhole leak on your radiator. A patchy warm radiator is also a good indicator as this implies the build-up of sludge that causes the cold spots on your radiator. However, pinpointing the exact location of the pinhole leak will require some finesse.

You would need to dry your radiator, as it is near impossible to discern the source of the leakage when the radiator is wet. A dry towel would be helpful while drying the radiator, then use dry paper, preferably tissue paper.

How to locate a pinhole leak in copper pipes

Pinhole leaks along the ducts can be virtually impossible to detect. Unlike the radiators in open spaces, pipes usually run in hidden places like under a floor or in a wall. This type of pinhole leak is the most destructive because it is detected after extensive damage.

Here are some of the tell-tale signs that should alert you to the presence of pinhole leaks along your pipework:

  • A sudden increase in your water bills.
  • Discolouration of your copper pipes.
  • Watermarks on walls or ceiling.
  • Moisture on exposed pipework.
  • Dripping sounds.

How to fix pinhole leaks

There are different ways of fixing a pinhole leak in a central heating radiator depending on the extent of the damage. The best way of securing a radiator would be to shell out a replacement. This method is expensive and will undoubtedly leave a dent in your pocket. Alternatively, you can use a sealant to fix the leak.

Fixing a pinhole leak using a leak sealer

The easiest way of solving a pin-prick leak is to add a leak sealer solution into the central heating system. You can introduce the sealant into the system by adding it to an almost empty header tank. Next, open the drain cork and let the cured water with the leak sealer back into the system.

The sealant should have been distributed evenly around the system within 24 hours, and it should start to take effect.

Fixing a pinhole leak using a radiator epoxy

If you prefer a slightly more in-depth solution, you can try the cold weld epoxy. It is applied to the outside of a leaky radiator to fix the holes.

To effectively fix pinhole leaks with a radiator epoxy, simply follow the following steps:

  1. Locate the pinhole leak – As earlier mentioned, locating the source of the leakage precedes any fixing.
  2. Turn off your water supply and drain your radiator – For this process to be successful, you will need to work with a dry radiator. A dry radiator will make it easy to detect the pinhole leak.
  3. Be ready with a towel and a bucket – It will help you collect any water that might escape during radiator pinhole leak repair.
  4. Completely dust, clean and dry the outside of the radiator – The radiator epoxy is usually more efficient when applied to a dry clean surface.
  5. Use epoxy putty on the surface of your radiator over where the pinhole leak is.
  6. Allow about 12 hours for the epoxy to dry before refilling the radiator and turning the central heating back on.

Replacing the radiator

If your radiators are highly corroded, old and previously sealed pinhole leaks are beginning to reopen and make even bigger holes, it spells trouble for you. At this point, sealants will not be effective, and if they are, they would only be a temporary fix. A more permanent solution is the hard truth of replacement.

It might seem expensive, but it will help with the efficiency of your boiler and prevent further damage from spillage in the long run. Replacing the radiator altogether will cost you anything from 100-200 pounds.

Prevention of future radiator pinhole leaks

You would not want the reoccurrence of pinhole leaks, especially after solving the problem yourself. Therefore, taking care of your central heating system will prevent the irreversible rot of your system. You can forestall the unprecedented events of a heavily contaminated system by performing power flush intermittently, ideally within five years.

The power flush will remove sludge from your system, thus reducing the chances of rust and corrosion. You can also add a rust and corrosion inhibitor to halt any rusting that has already started in your system.

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