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Why is my radiator leaking?

That moment when you notice water seeping from your radiator or a pool of water on the floor can make your heart sink. But worry not, in this guide we aim to answer the question: ‘why is my radiator leaking?’.

That moment when you notice water seeping from your radiator or a pool of water on the floor can make your heart sink. But worry not, in this guide we aim to answer the question, ‘why is my radiator leaking?’.

We’ll look at the common causes of why radiators leak and offer you some helpful advice and top tips for how to deal with the problem.

The first step to dealing with a leaking radiator is identifying the problem, and then seeking professional help from a plumber if needed.

Why does my radiator leak?

The common causes

There are a number of reasons why your radiator is leaking:

1. A leaky valve

One of the most common issues that cause radiators to leak is a damaged or faulty valve. Over time, radiator valves can suffer wear and tear so that the watertight seal loses some of its grip – causing water to leak out slowly.

Alternatively, it could be that the valve has not been tightened properly and allows water to escape.

Evidence of a leaky radiator valve – Pool of water underneath the radiator and potentially light water drips.

How to fix a leaking valve – To repair a damaged valve, you’ll need to drain the central system and fit a new valve and then, afterwards, bleed your radiator to get rid of excess air.

Alternatively, if you’re not confident in dealing with plumbing issues, contact a local plumber to fix the radiator valve.

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2. A corroded radiator

Another popular culprit for a leaking radiator is rust. Corrosion can happen in the inside of a radiator over time and, if left untreated, can lead to holes at the bottom of the radiator.

Radiator leaking water from the bottomThe corroded holes usually start very small but can easily worsen to become an emergency, if ignored. Rusting is often an issue for old radiators, particularly those that haven’t had anti-corrosion chemical inhibitors added to the radiator water.

Evidence of a corroded radiator – Any pool or dripping water will be brown in colour.

How to fix a corroded radiator – If your radiator is rusted to the point that it’s leaking you’ll most likely need to replace the whole radiator unit. You can find out more in our guide on how to replace a radiator, but it’s not a job for an amateur DIY enthusiast.

To avoid issues with poor radiator installation that can lead to leaks and other issues, we always recommend hiring a qualified plumber to carry out any radiator replacement work.

3. Loose or damaged radiator spindle

The radiator spindle, which is the joint that connects the valve to the main radiator unit, can often cause a leak. Most of the time it’s because the spine has come loose and simply needs tightening, but it also may be damaged and need replacing.

Evidence of a loose or damaged radiator spindle – Water leaking from the spindle itself.

How to fix a radiator spindle – If the spindle is loose then it’s a case of tightening it, which should fix the problem. If, however, the radiator spindle is damaged then you’ll need to replace it with a new spindle.

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Common damage caused by radiator leaks

If you’re tempted to simply mop up a bit of water every now and then, instead of fixing your leaking radiator, think again. Here are some of the issues that a leaking radiator can cause:

  • Damage to flooring and, if left untreated, leaking to lower levels of your home
  • Risk of an electrical hazard if water leaks to any nearby electrical points
  • Reduced heating capacity due to a negative impact on your radiator’s BTU heat output
  • Increased energy bills due to poor heating efficiency

Plumber replacing a leaking radiatorHow much does it cost to replace a radiator?

The average cost to replace a radiator in the UK is around £200 – £300, depending on the size, style and location of your radiator. If you plan on removing and repairing your existing radiator, instead of replacing it with a new radiator, the cost is around £125.

To find out more, read our guide on the cost to remove and replace a radiator. Or, to see details for other plumbing work, check out our guide to plumber costs.


Why is my radiator leaking from the bottom?

In the majority of cases, a radiator that is leaking from the bottom will be the result of an issue with either the radiator valve, spindle or rust damage. If you’re not confident in investigating the issue yourself, a local plumber will be able to identify the root cause of your leaking radiator and repair or replace it for you.

Why does my radiator keep losing water?

Your radiator will most likely be losing water because the valve or spindle is loose, or damaged. Or, alternatively, the inside of the radiator has rusted and caused small holes that are allowing water to leak out. If in doubt, contact a qualified local plumber to come and inspect your radiator. An experienced plumber will be able to quickly locate the issue and offer a solution.

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