How to fix a boiler

How to Fix a Boiler Without Opening It: 6 Easy Tips to Help

Last updated on January 29th, 2024

Having your boiler not fire up or a leaking boiler can be a nightmare, especially on a cold winter’s night.

Fixing your own boiler is possible as there are certain problems anyone can fix.

I have been fixing boilers for over a decade and these are some of the most simple boiler repairs I come across that most people can do.

These are totally safe repairs and do not require you to go inside your boiler, which you should not do if you’re not competent.

How to Fix a Boiler

Learning how to fix a boiler can save you money and from having to be without heating and hot water waiting for a gas engineer to come.

These are some common boiler problems that anyone can fix:

  1. Low boiler pressure
  2. No power supply
  3. Thermostat problem
  4. Radiators need bleeding
  5. No gas supply
  6. Frozen boiler condensate pipe

Low Boiler Pressure

Low boiler pressure is a simple DIY boiler repair that’s often needed. When your boiler pressure is low then the boiler will stop working. You need to repressurise the boiler.

If you have a gravity-fed heating system, with a small header tank in the loft, then it won’t be a pressure problem you have as it’s not a pressurised system.

Worcester boiler pressure low
Low boiler pressure

How to fix low boiler pressure:

Find the Pressure Gauge

First, you will need to find the pressure gauge on your boiler, it could be on the expansion vessel if you don’t have a combi boiler. 

The expansion vessel is normally located in the same cupboard as the hot water cylinder tank.

Once you have found the pressure gauge, you need to make sure it’s between 1 and 1.5 bar.

Top The Pressure Up

If it’s on less than one bar, you need to top the pressure up using the boiler filling loop and then reset your boiler.

The filling loop will either be on the bottom of the boiler, the pipework underneath, or it could be in the hot water cylinder cupboard.

A filling loop usually has two black handles that you need to open, and then close when you’ve reached the correct pressure on the gauge.

Topping the pressure up is one of the boiler repair tips that everyone should learn so you know how to fix the pressure on a boiler.

If your boiler loses pressure regularly, you most likely have a leak, an expansion vessel problem, or a pressure relief valve problem.

No Power Supply

If you are not getting any sign of life at your boiler, like no lights or screen working, then you should check that you are getting electrical power to the boiler.

No power supply to boiler
Fused spur switch for boiler

Check The Fused Spur

The first place to check is the fused spur switch which should be next to your boiler. A quick fix could be as easy as flicking the switch back on, as these can get knocked off accidentally. 

The fuse (must be 3a) in the spur could have also blown which will need to be replaced if it has.

Check The Fuse Board

If all is good at the spur then you can check the electrical consumer unit (or fuse board) to make sure that hasn’t tripped your heating circuit.

Your fuse board is where all the electrical circuits are controlled and where the fuses and circuit breakers are.

Check if the boiler’s circuit has tripped and if it has, turn it back on. If it keeps happening you should call an electrician in to get it checked out.

Thermostat Problem

Thermostat Problem
Room thermostat

Is it Turned Up?

Room thermostats turn the boiler off when the room that the thermostat is in has reached the temperature you have it set at.

If the room temperature is 14 degrees and the thermostat is set to 13 degrees, then the boiler won’t come on.

Yes, this does happen…

So make sure it’s turned up!

This could save you from paying the boiler repairer a call-out fee for doing next to nothing, and also save you from looking silly.

Are The Batteries Dead?

Wireless thermostats and programmers are powered by batteries, so you should always check them when you’re having boiler problems.

I have been called out to boiler breakdown repairs where the customer did not realise their thermostat was wireless and therefore didn’t know it needed batteries.

Just open it up and replace them with the same type of batteries, normally AA or AAA batteries.

Smart thermostats, like Hive, will email you when your batteries are running low so you don’t need to worry about them running out fully if you have a smart thermostat.

Radiators Need Bleeding

Bleeding the air out of each radiator is a very important DIY boiler repair you should learn to fix your boiler problems.

How to bleed a radiator
Bleeding a radiator

Bleeding a radiator is simple, all you need is a radiator bleed key.


You could have an airlock in your heating system which is causing your boiler to not work. Or, the boiler might be working, but the radiators are not getting hot because there isn’t any water in them.

You should check all of your radiators for air by bleeding them at the radiator bleed valve with a bleed key.

You might need to bleed the air from the vent in the hot water cylinder cupboard if you don’t have a combi boiler, you will probably need some water pump pliers to do this.


If you bleed any air out of the radiators that means you’re releasing pressure from your heating system. You will need to keep topping the pressure back up at the filling loop.

No Gas Supply

Check the Emergency Control Valve (ECV)

The ECV is the handle on the steel pipe next to the gas meter. Gas meters are sometimes located in cupboards under stairs and kitchen cupboards.

gas meter ecv
Gas meter and ECV

They can (and do) get knocked off accidentally with coats, bags etc. Check this is turned on. The handle should be in line with the pipe when it’s turned on.

There should also be some yellow tape telling you which way is on and off. Make sure it’s turned on.

Prepayment Gas Meters

If you have a pay-as-you-go gas meter card or key to put money on, make sure you have money on it.

Also, if you let them run out of money completely, it can sometimes be quite tricky to get the gas through again. So, you may need to call your gas supplier to get this sorted.

Frozen Condensate Pipe

Having a Frozen condensate pipe will cause the boiler to stop working. If it’s below freezing outside and your boiler stops working, then there is a good chance it’s because the condensate pipe has frozen.

To fix this you will need to thaw out the pipe by pouring warm water over it until it’s not frozen then reset the boiler.


I hope these DIY boiler repair tips can help you to fix your boiler. Most of these checks will be included on a boiler service, but they are simple things you can check for yourself.

You might have to bite the bullet and ring a local boiler repair engineer if you can’t fix your problem.

Feel free to ask any questions in the comment section below and I’ll try my best to help.

Please share this post if you find it helpful.


  • Steven Reid

    I am a full-time plumber and Gas Safe registered engineer. I incorporated Housewarm Ltd. in 2011 to provide heating and plumbing services to homes in Newcastle upon Tyne, England. I now blog about what I've learned over the years to help DIYers and plumbers.

    View all posts
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