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Most Common Boiler Problems

And how to fix them…

A sudden issue with your boiler is never ideal. There are few things more inconveniencing than having to go without the heating and hot water you need for your home.

Below we have put together 10 of the most common boiler issues and outline their potential causes. We’ve also mentioned possible solutions.

  1. Leaking
  2. Low boiler pressure
  3. No heating or hot water
  4. Frozen condensate pipe
  5. Radiator faults
  6. Boiler not responding to thermostat
  7. Gurgling, banging, or whistling noises coming from your boiler
  8. Pilot light keeps switching off
  9. Boiler wont turn on
  10. Boiler breakdown


A boiler leak is usually caused by an issue with the internal component, such as pressure valve and pump seal. Its likely your pressure has become too high if leaks stems from your pressure relief seal. If the leak is caused by a problem with the pump seal, there’s a high chance the seal has worn out.

A leak that has developed around your systems pipes could be caused by corrosion. There could also be an issue with the way your system was installed. Its recommended that you get a gas safe engineer to identify and fix the issue. If the leak is caused by a serious fault, your engineer may recommend you get a new boiler installed.

Low Boiler Pressure

By taking a look at the built in pressure gauge, you can usually identify if your boilers pressure is too low. Your boiler pressure should be at the 1.5 bar. If it gets below 1 your boiler will not be able to function properly.

There are many causes to why your boiler pressure is low, such as a system leak, recently bled radiators, a failed component, or a broken seal. To identify the issue you could look for visible signs of a leak. You shouldn’t remove any castings from the boiler. Call a gas safe registered engineer if you discover a leak and they will be able to fix it safely. If there’s no signs of a leak you could try re pressurizing your boiler yourself, if you feel comfortable to do so.

No heating or hot water

This issue can be caused by anything from faulty motorized valves, broken system diaphragms and airlocks, to low pressure, or a broken thermostat.

To see if this issue is caused by low pressure, you should check your pressure gauge to see if it is below 1. If it is it may need repressurising. If the heating or hot water is caused by an issue with your thermostat, check the devices manufacture guide for a possible solution. If none can be found, contact your manufacture for additional help.

If you still haven’t found a solution we recommend getting in touch with a trained engineer as issues such as a broken motorized valve or a faulty diaphragm will require a professional.

Frozen condensate pipe

This issue is very common in the colder months. Your systems condensate pipe is responsible for transporting the condensate from your boiler to your outside drain. During periods of cold weather the condensate can freeze and cause blockage to occur. This is most common in homes where the condensate pipe is fitted externally or in an unheated area, such as a garage. This issue could cause the condensate to revert back up to the boiler and lead to the system breaking down.

Radiator faults

Cold patches and other problems are usually caused by a build up of air or sludge inside of your radiators. This can cause heat to be distributed unequally. Cold patches in different areas can indicate different kinds of issues.

Most radiator issues can be resolved by bleeding the radiators. This is a simple task that can be carried out yourself.

Boiler not responding to thermostat

If the clocks have gone back or forwards recently you should make sure your boiler is in line with the correct time. If your boiler is completely failing to respond to your thermostat the controls may be broken or old. However there’s a few checks that you can do before going ahead with it being completely broken.

  • Try replacing the batteries
  • Position the device closer to the boiler
  • Look at the instructions booklet
  • Contact the manufacturer

Noises coming from your boiler

Its normal for your boiler to make noise, especially if its firing up. If your boiler suddenly begins to make unusual gargling, banging, or whistling noises, we recommend getting in touch with a trained engineer.

Unusual boiler noises can be caused by air in the system, a faulty pump, low water pressure, or even a build up of lime scale, knows as (kettling).

Pilot light keeps switching off

Older boilers may have a permanent pilot light which needs to stay lit in order to light the larger burner within your boiler. If this light keeps going out there could be a faulty thermocouple that is cutting off the gas supply. Alternatively, there could be a deposit build-up or a draught blowing the light out.

You could try to reignite the pilot light yourself if you are comfortable doing so. Please follow the instructions in your boiler manual. Before you do this, you should ensure that your gas stopcock is on and that there are no issues with your gas supply, you can check other gas appliances to confirm this. We recommend contacting a Gas Safe registered engineer to help solve this issue.

Boiler wont turn on

If your boiler won’t turn on, the first thing you should do is check other appliances and power supplies in your home to see if they are working.  If they are, check your fuse box to see if any switches have failed or tripped. If you still cannot find the cause, we recommend getting in touch with a trained engineer.

If your boiler is turning on but keeps going off, the pressure could be low or there could be a blockage that is inhibiting the system. Check your system’s pressure gauge and depressurize the boiler if it is set below 1. Alternatively, contact a Gas Safe registered engineer.

Boiler breakdown

If your boiler breaks down and is left unaddressed, all of the above issues can eventually lead to a complete boiler breakdown. In which case you should contact a gas safe engineer as soon as possible.

Age and inefficiency can also cause boilers to break down beyond repair. If you have an old inefficient boiler, we recommend investing in a completely new system so that you can get the heating and hot water you need. A new modern and energy efficient boiler could also help you save on your energy bills.

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