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What to do when your boiler starts leaking

If you’ve searched ‘boiler leaking’ and reached this article, it’s probably because there’s water dripping, or even pooling, from your boiler. It doesn’t take an expert to know that’s not a good sign!

Your boiler dripping water indicates that there’s something pretty wrong with it, and it’s not something you should ignore. It could be caused by several internal factors, such as a broken seal or valve. Sometimes a leaking boiler will have an easy (and cheap) fix. Other times problems can be terminal. This is why locating the source of the problem and repairing it quickly is paramount. The quicker you act, the less chance there is of your boiler components rusting or electrical parts shorting, which can be detrimental to your boiler.

Here we’ll share the steps to take if you notice your boiler leaking but remember a Gas Safe registered engineer should always carry out repairs on your behalf.

Boiler leaking water from the bottom?

Take a look under your boiler to see if you can spot where the leak is coming from. If it’s a large leak, it’ll be easy to identify. If there’s only a small amount of water dripping from boiler, you may need to feel around the pipework to see if it’s wet.

Poorly installed or corroded pipework is usually the cause of a boiler leaking water. If your boiler is newly installed, the joints in the pipework may need checking, as it’s likely they haven’t been fitted quite right. However, if your boiler is older (especially if it’s over 10 years), it’s more likely to be corrosion in the pipework. Corrosion, caused by a mix of water and metallic debris, will create tiny gaps in the copper piping and allow water to escape – hence your boiler dripping water everywhere.

Unfortunately, if there is a leak underneath your boiler, it’s not something you’re going to be able to fix yourself. You’ll need to call out a registered gas engineer to repair it for you. In the meantime, we’d recommend placing a bowl, or if there’s room, a bucket, underneath your boiler to contain the leak. If you can identify the pipe that is leaking underneath your boiler, you may also want to wrap a small cloth or towel around it to prevent excess dripping.

Could the boiler pressure be too high?

Don’t like working under too much pressure? Neither does your boiler. If the pressure is too high, it means there’s too much water in the system and the pressure release valve will attempt to get rid of it. If that fails, the internal parts may stop working properly and result in a leaking boiler.

If you think high pressure may be the cause of your boiler dropping water, you can take action yourself. First, check the pressure gauge on the front of your boiler. You’ll notice a green section. This is where the pressure gauge should sit, with combi boilers and system boilers at around 1 bar. If the pressure gauge lies beyond the green bar, it means your boiler is over pressurised.

With a little confidence and a couple of tools, you should be able to fix this problem yourself, with a technique you’ve probably heard before, called ‘bleeding.’ First, make sure that the filling loop tap on your boiler is firmly closed. This is located underneath your boiler and will look like a silver pipe with one or two taps. Make sure both taps are closed.

Next, you’ll need to bleed your radiators. Grab a radiator key and a bucket, bowl or Tupperware (whatever you have handy) to catch the water. Use the key to loosen the nut on the end of your radiator and it’ll release the excess water in your system.

Leaky seals

If your boiler is leaking internally, it may be that the seals have failed. Sometimes this is caused by an over pressurised boiler (as mentioned above) but more often it’s down to a lengthy process of decay.

You can check for internal leaks by removing the cover of your boiler. We suggest following the ‘look but don’t touch’ rule. If you can spot where the seals are failing, you’ll be able to let the gas engineer know, and they’ll be able to stop the leak even quicker.

If the issues are only minor, they can be resolved quite quickly and cheaply with new seals. However, if the corrosion has caused more substantial sealant issues, repairs can become expensive and it may be more cost-effective to buy a new boiler.

Faulty heat exchanger

If a faulty or leaky heat exchanger is the root of your boiler leaking problem, we’re afraid to say, it’s curtains. Unfortunately, heat exchangers are pretty expensive to replace. It’s more cost effective to buy a new boiler and benefit from greater efficiency in the long term.

Faulty heat exchangers are common in old models and cheaper boilers lacking in quality. You won’t be able to identify this problem yourself, so you’ll need to contact a gas engineer to take a look for you. Prepare for the worst, and then it’ll be a nice surprise if it’s a cheap fix instead!

Leaking boiler overflow pipe

If the leak isn’t coming from your boiler but rather the boiler overflow outside your house, it’s likely there’s a problem with the float valve. This is the mechanism that looks like a metal arm with a plastic ball on the end. It’s found in your loft tank and used to control its water levels.

The float valve will likely need to be replaced. You may also find that the washers need refitting too. Unless experienced in this sort of thing, it’s always best to contact a heating plumber to complete the repairs to a high standard and give you total peace of mind.

Is a leaking boiler an emergency?

A substantial leak suggests there’s something seriously wrong with your boiler. If it’s leaking from the bottom of the casing, the water has probably come into contact with electrical parts, which is never a good thing. But is a leaking boiler dangerous to you? Providing you don’t poke around in your boiler and call a registered gas engineer to carry out the work, you should be just fine.

The quicker you identify and deal with boiler leaking problems, the more likely you are to save your system. Follow these simple steps:

  • Attempt to safely identify the location of the boiler leak
  • Use a cloth, bowl/bucket to collect dripping water and prevent further damage
  • Correct pressure gauge (if necessary)
  • Get in touch with a registered gas safe engineer

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