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Why is My Boiler Leaking? 7 Possible Causes


First things first, if your gas boiler is leaking water do not attempt to fix it yourself by tampering with pipework or seals.

Only Gas Safe registered engineers should be working with your heating system as accidentally disturbing the gas supply can have potentially lethal consequences. In addition, a leaking boiler can be particularly dangerous as the leak may lead to corrosion and rust, or can cause the boiler’s electrical components to short circuit.

If you find your boiler (or central heating pipework) is leaking you should:

  • Turn off the mains water supply
  • Switch off the heating
  • Clean up any water
  • Contact a professional heating engineer.

A professional will be able to diagnose the problem quickly, repair it effectively and advise you how best to prevent it happening again.

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What’s Causing Your Boiler to Leak?

The cause of your leaky boiler may be able to be diagnosed based on where the water is coming from but it’s always best to seek professional advice to ensure you get the right solution as quickly as possible. Here are 7 of the more common causes of a leaky boiler:

1. Your Boiler Pressure is Too High

If boiler pressure is too high then there is too much water being pushed through your heating system and the boiler needs to find somewhere to release the extra pressure to prevent the unit itself exploding. Your boiler pressure should be set between 1 and 2 on the pressure gauge. If it is over 2 then it is probably too high and you should use the instructions in the manufacturer’s manual to reduce it. If you’re in any doubt at all about how to do this, contact a professional engineer.

2. Your Boiler’s Temperature is Set Too High

A leak from the temperature valve could mean that the boiler temperature is too high and, in addition to a leak, could lead to dangerously hot water coming out of the taps. A boiler is usually fitted with a temperature control valve (TCV) which monitors the temperature of the water in the boiler and prevents it from getting too high.

3. You Have Corroded Pipes or Hot Water Tank

Over time your pipework could begin to corrode and weaken leading to a leak in one or more places. Depending on how many parts of the system have corroded, it’s possible that simply replacing one section could solve the problem. If the corrosion has spread you may need to invest in a new boiler.

4. There’s a Broken Seal on the Boiler Pump

Your central heating includes a boiler pump which pushes hot water around the pipes and radiators in your home. If it isn’t sealed properly water may begin to leak out.

5. There are Loose Pipe Connections

It’s not a fault exactly but the natural heating and cooling of water that goes on in your heating system means water is expanding and contracting in your pipes all the time. This can lead to loosening of joints and connectors and these may simply need to be tightened.

6. Your Central Heating is Over 10 Years Old

If you’re boiler is 8 -10 years old (or even older) it may be that it’s simply come to the end of the road. Installing a new boiler may be the best solution not only to stop the leak but also to increase the energy efficiency of your home, helping to save you money on your bills.

7. The Boiler Has Been Installed Incorrectly

If your boiler has been fitted incorrectly then problems like a leaky boiler or pipework are very likely to occur eventually. Gas boilers should always be installed by Gas Safe registered heating engineers.

If you need help with a leaky boiler, other repairs or you need a new boiler, you can visit Boiler Guide to get free installation quotes from up to 3 Gas Safe engineers in your local area.

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My Boiler Was Leaking But Has Now Stopped. Why?

When you turn either the heating or your water supply off, the leak will stop. However, if you haven’t done this but a leak seems to have disappeared, it may due to heavy rainfall. If you have a poorly fitted flue then water may be leaking into the boiler from the outside. A professional engineer will need to reinstall the flue.

Does a Leaking Boiler Cause Low Pressure?

As well as the leak you may also notice that your boiler has lower pressure. This will affect how efficiently the boiler operates and could cause it to automatically shut down completely, so the leak needs to be dealt with as soon as possible.

Is a Leaky Boiler Dangerous?

Yes, for a few reasons. A leaking boiler is not only inconvenient it may also mean that water is leaking into electrical components in the boiler. It could also could cause damage to your boiler or home from the carpets, furniture and belongings to long term structural damage.

Preventing a Boiler Leakage

Just like a car, your boiler should be serviced annually by a Gas Safe engineer. They will check that everything in your heating system is working effectively and safely and should be able to catch small issues before they turn into bigger problems like leaks.

Can You Fix a Leaking Boiler?

We may sound like a broken record, but never attempt to fix your boiler yourself! A bodged DIY job will not only end up costing you more money and hassle in the end but could also be potentially very dangerous. A Gas Safe registered engineer will be able to diagnose and repair your leaky boiler quickly and, if you compare prices from several engineers in your area, you could get the problem fixed for a lot less money than you think.

The easiest and quickest way to find and compare quotes from a few different installers is to use comparison sites like Boiler Guide. You simply complete one form and they’ll find you free quotes from up to 3 trusted engineers in your local area. You’ll then be able to compare the quotes and choose the best one for you. There’s no obligation to use any of the quotes if they’re not right for you.

Get FREE Boiler Quotes

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