How to fix a pinhole leak in your radiator and copper pipes

8 December 2020
How to fix a pinhole leak in your radiator and copper pipes

A pinhole leak in your rads or pipes is an annoying problem. Not only can it cause your heating system to perform less efficiently, it can also lead to expensive water damage if left untreated.

In this article, we'll look at what causes a pinhole leak and how you can go about fixing it and solving the problem.

What causes pinhole leaks?

If a central heating system is not regularly maintained, then corrosion can occur in your pipes and, in particular, your radiators.

Over time, tiny flakes of rusty metal can flake off into your system and settle at the bottom of radiators or certain areas in your pipework. These shards of rust compact and form a brown sludge which slowly eats away from the inside out.

If the problem is not dealt with then the corrosion eventually reaches the outside of your radiators or pipes, creating tiny holes from which water can leak.

How to locate a pinhole leak


A pinhole leak in a radiator is usually easy to spot because there will usually be a wet spot on the floor underneath.

You might also notice that the bottom of the radiator is not getting hot due to a build up of sludge inside.

Copper pipes

Pinhole leaks in copper pipework can be much more difficult to locate as they could be occurring out of sight under a floor or in a wall.

These types of pinhole leaks can be the most dangerous as they are often not discovered until an expensive amount of damage has already been done.

Some tell tale signs that you have a leak in a copper pipe are:

  • Sudden increase in your water bills
  • Discolouration to your copper pipes - often green or black dots
  • Water marks on walls or ceilings
  • Moisture on exposed pipework
  • Dripping sounds

Fixing pinhole leaks

Leak sealer

Fernox leak sealer

The simplest way to fix leaks in your copper pipes or radiators is to pour a leak sealer solution into your central heating system.

This can be added to an almost-empty central heating header tank, opening the drain cock and adding back into your system until all the leak sealer is circulating.

You then need to switch on your heating system to ensure that the leak sealer flows evenly around your system. It should start to take effect and seal u small holes in your system within 24 hours.

Radiator epoxy

Cold weld epoxy bond

For a slightly more in depth solution, you could apply some cold weld epoxy to the outside of your leaky radiator in order to fix the holes.

You'll need to drain the radiator and then clean the the surface around the holes so that the epoxy bonds to the rad. Apply the epoxy to the holes according to the manufacturer's instructions and allow to dry thoroughly.

Once dry, you can then refill the radiator and the leak should hopefully have stopped.

Replace radiators and pipes

White Classic Column Trade Direct Radiator

If your radiators or pipes have corroded so much that they are leaking then fixing with a leak sealer or epoxy is likely to only fix the problem temporarily.

You may well have corrosion in other areas or the previously-fixed holes may corrode and reopen again.

If you know your radiators and pipework are old then you might want to consider having them replaced.

While this does has an upfront cost, the potential water damage from leaky pipes and radiators could cost a lot more to fix, and would probably be considered an emergency.

If you do upgrade your rads and pipework, you'll probably notice your energy bills are cheaper as your system is running much more efficiently.

How to prevent future radiator pinhole leaks?

Now that you’ve put in the hard work to fix the pinhole radiator leaks, the last thing you want is the dregs, corrosion, or gurgling pipes to return.

Don’t let your central heating units and pipes irreversibly “rot” from the inside. My Plumber radiator repair professionals advise you to forestall unwanted fiasco of a heavily contaminated system when you perform power flush every 5 years or once you get a new boiler installed. While the power flush process makes your radiator system sludge-free, adding a rust and corrosion inhibitor is a smart move to provide an added protective layer inside the radiator, halt the process of corrosion, and boost central heating efficiency. 

To cleanse the radiator dirt and scum proactively is worth every minute. This is a proven, cost-effective way to prolong your central heating life, prevent blockages, and minimise the risk of radiator replacement. 

Call a professional

As with everything to do with your plumbing and heating system, if you are not sure what or where the problem is, it's always best to call in a professional.

Water can cause huge amounts of damage to a property as small leaks tend to quickly become large leaks. If you do suspect that something is leaking then call in a professional to deal with the problem quickly.


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