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What are the most common boiler faults that need repairing?

Boiler Strange Banging, Whistling or Gurgling Noises emergency repair

Leaking & dripping

There are a few reasons why your boiler is making odd noises, it could be air in your system, water pressure too low, Imminent pump failure or it’s kettling.

You might be able to determine the type of problem your boiler is having based on the type of noise it’s making. For example, a noise like a boiling kettle is usually a result of Kettling.

Boiler not working cold water instead of heating up

No heat or hot water

Boiler not working? The first thing you should check is your boiler pressure and thermostat.

If your boiler pressure is normal and your thermostat is set correctly then it will likely be internal component failing. If that’s the case and you can’t get the boiler working, we suggest getting a Gas Safe engineer to repair your boiler.

This will range in price as a number of things could potentially be wrong with your boiler, but to identify the issue there will be a call out charge of at least £50 - £60.

Boiler pilot light has gone out in need of a repair

Pilot light has gone out

Your pilot light is a small gas flame that will ignite a more powerful gas burner, to help your boiler heat up quickly. If your pilot light is out then it’s likely automatically shutting down the gas supply.

It’s very important that you check there aren’t any issues with the gas supply. If your gas stopcock is turned on but your boiler and gas appliances aren’t working, then you should immediately contact your gas supplier.

If this isn’t the case, your pilot light igniter may be broken and in need of replacing. Always seek the help of a Gas Safe engineer to replace any parts that involve gas work.

Estimated replacement cost of a new thermocouple £100 +

Boiler lower pressure on gauge easily fixed

Low boiler pressure

A quick pressure check is simple, just go to your boiler and look at the gauge meter. If your needle is below 1, then you likely have low boiler pressure which could be caused by a water leak somewhere in your system.

If you can’t find any visible leaks you may be lucky, and it just needs to be repressured. This is something you can do by checking your boiler manufacturers website and finding the section on how to repressure your boiler model. 

If you don’t feel comfortable doing this, you can always call a Gas Safe engineer to sort it out.

Kettling boiler in need of a chemical flush for sludge build up


If your boiler is making a strange bubbling noise (like a boiling kettle) you could have a build-up of sludge in your boiler’s heat exchange, causing a restriction of water which begins to overheat & steam.

Kettling is a common occurrence in areas with hard water, causing your boiler to work harder & often shortening its lifespan - unless your boiler is flushed professionally.

This isn’t a major issue, but we would recommend getting a Gas Safe engineer to flush out the system which will clear out the build-up of sludge and will help efficiency.

Estimated system flush cost of £300 + depending on how many radiators you have in the home.

Boiler leaking water in need of emergency repair

Leaking & dripping

If your boiler is leaking water, we recommend you call an engineer as the most common cause for a leak is a broken internal component.

This may be due to the pressure being too high inside your boiler causing a valve or pump seal to be worn out – unfortunately, this means a part will need replacing.

The estimated replacement cost is £250 +

waste gas pipe frozen causing errors in the boiler

Frozen condensate pipe

All condensing boilers have a pipe which transports acidic water away from the boiler. This condensate pipe is usually a 2cm wide white pipe that leads outside the property into a drain – this pipe is well known for freezing in the winter months.

We’ve created a handy step by step guide to fix your frozen condensate problem here.

Our guide is simple to understand and you won't need to get a professional involved, this is absolutely something you can do in 5 minutes with immediate results.

Thermostat error causing boiler to shut down or turn off too soon

Thermostat issues

If your thermostat is turning your heating on or off when it’s not supposed to – it may be time to invest in a new one.

If you’ve already checked your thermostat is set up correctly and you’ve not recently changed any settings, your thermostat could think your home is warmer than it is.

To rule out this possibility, try increasing the temperature slightly, if the heating comes on but says it’s a lot hotter than it actually is, you’ll know the thermostat is experiencing a heating error. An electrician can easily fix this issue.

If that didn’t work, your thermostat has likely malfunctioned and you'll have to consider a replacement.

Estimated cost for a brand-new thermostat ranges from £90 - £200 depending on make and model.

Radiator not heating up due to needing to be bled or chemically cleaned

Radiators not heating

If only the bottom of the radiator is getting hot you may need to bleed it - bleeding a radiator is a fairly simple process you can do yourself.

If certain radiators aren’t getting hot in your home, then your radiators could need a re-balance. You can do this with simple adjustments of valves on all the radiators - this will help to ensure each radiator is getting enough hot water to work effectively.

If your radiators aren’t heating up at all, you may have a build-up of sludge in your system that is preventing the flow of hot water to the radiators.

You’ll need to get in touch with a Gas Safe Engineer to remove the build-up by chemically cleaning your system.

Estimated chemical flush cost of £300 + depending on how many radiators you have in the home.

Boiler turning itself off due to errors or needing repair work

Boiler keeps turning itself off

A boiler that keeps turning itself off could be doing so for many different reasons. For example, it could have low water pressure, a technical issue with your thermostat, or a frozen condensate issue.

Check the other faults above to see if you can fix your boiler before getting a gas safe registered engineer to come out and repair your boiler.

Get Your Boiler Repaired Now

Here at Boiler Plan, we offer a repair service for £60 for the first hour and £45 for every hour after that. You’ll only pay list price for any replacement parts, so it’s an extremely affordable service.

Should you repair or replace your boiler?

In general, it costs less to repair a newer boiler than a model that’s over 10-years-old. The problem with older boilers is that parts are often harder to come by – so finding and buying them costs a lot more.