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Switching your Boiler Back on after Summer - How to Avoid a Breakdown.

Becky Mckay
By: Becky Mckay
Updated: 17th June 2022

The kids are heading back to school and memories of staycations, BBQ's and lazy sunny afternoons (not that the weather has been particularly nice) are fading and before we know it, the nights will be drawing in and we'll be switching the boiler back on in time for the winter.

The first week in September marks the first boiler switch on after the summer and for many homeowners this can lead to heating problems.

David Holmes, founder at home heating experts Boiler Guide says:

“At this time every year without fail, our website gets inundated with enquiries from customers frantic to resolve their heating problems before the winter kicks in. We see a 65% increase in web traffic and enquiries from customers looking for new boiler quotes or repairs. After a summer of inactivity, older boilers often struggle to spark back into life and naturally problems can occur.”

So if you are tempted to flick the switch this week, Boiler Guide has put together a few pointers for successfully restarting your boiler after summer.

Start with a boiler service

Your boiler should be serviced every year by a Gas Safe registered engineer.

A boiler service will bring any potential faults to the attention of a professional before it starts to get really cold. That way, you shouldn’t be left with a broken boiler when you need it the most.

Gradually switch your boiler back on

If your boiler’s been off during the summer, you should have been aiming to fire it up once or twice a month to help prevent a build-up of debris.

This will also flag up any potential issues before switching back on permanently when the weather gets colder.

If you haven't been doing this and as it's not too cold yet you could still fire it up a couple of times over the coming weeks.

Bleed your radiators

You’re unlikely to notice if your radiators have stopped working effectively over the summer because they’ve probably not been on.

If you find that one or more of your radiators isn’t heating up in certain areas (or not warming up at all) then you might need to bleed your radiators to remove trapped air.

When it comes to radiators, it’s also worth noting that thermostatic radiator valves can get stuck if they’re left closed for too long which means that they won’t work when it comes to turning the heating on again. Try to keep them open as much as you can during the summer months.

Don't turn the heat up too fast

It can be tempting to crank the heat up as soon as we start feeling the cold.

But doing this could mean you set the temperature higher than necessary and end up wasting both energy and money.

Instead, try to turn your heating up one degree at a time. Generally, your thermostat should be set at a temperature you feel comfortable at. For most households this is between 18 and 21 degrees celsius (and slightly higher for the elderly).

It's also important to remember that turning a thermostat up won't make your home heat up any faster, it will just reach a higher temperature.

Check for any boiler problems

During a long period of inactivity (over the summer) is when problems with your boiler are most likely to happen.

Low boiler pressure

If your boiler’s pressure is too low then it won’t fire up.

You can read the boiler pressure by looking at the pressure gauge. Ideally, it should be somewhere between 1 and 2 Bar. Any lower than 1 and your boiler has low pressure.

Fortunately, increasing the pressure is something you can do yourself. Take a look at this guide to increasing boiler pressure.

Before you do increase the pressure, check the heating system for any signs of leaks. If you do spot a leak – no matter how small – turn the mains water supply off and call a heating engineer.


If you notice a sound like a kettle when turning the heating on, this is a strong sign of kettling. An issue that’s caused by a build-up of sludge or limescale on the boiler’s heat exchanger.

A build-up of this nature can restrict the flow of water within the heat exchanger, causing it to overheat, steam and boil.

If this is the case, then you’ll need a heating engineer to clean out the heat exchanger. They may also recommend a magnetic filter which will capture any debris before it has a chance to build-up.

David Holmes said: 

"If all else fails and you do need to replace your boiler there are lots of benefits to soften the blow. Modern efficient boilers can save you up to £300 on your energy bills and will come with a warranty for a bit of extra peace-of-mind. Remember, if you are replacing your boiler,  always ensure you contact a Gas Safe registered engineer."

Becky Mckay

About the author

Becky Mckay

Becky is one of our home heating and renewable energy experts and has a wealth of experience writing about the world of heating.

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