'I’m a heating expert – here’s how to save £150 by fixing your radiators yourself'

New figures from BOXT reveal that nearly a third (30%) of Brits are stuck with central heating that doesn’t work properly - leaving rooms colder than they should be.

Alarmingly, up to 4 million* adults (10%) are also living in freezing conditions where none of their radiators work or heat up properly.

The survey of 2,000 UK adults revealed a quarter (25%) struggle with sluggish systems with radiators that take an age to warm up, making chilly mornings even worse.

And one in ten (10%) are forking out extra on electric heaters just to stay warm in rooms where the central heating isn’t doing the job.

Whether it’s cold at the top, chilly at the bottom, or not warming up at all, don’t panic - many radiator issues are easier to fix than you might think, and learning how could save you up to £150.

Ryan Gill, Lead Technical Engineer at fixed-price boiler specialist, BOXT, shares his top tips for troubleshooting common radiator problems so you can keep your home cosy without breaking the bank.

Why aren’t my radiators heating up?

Gill explains that most radiator issues fall into a few simple categories. The good news is that many of these problems can be solved without professional help. Here’s what might be going wrong:

1. Trapped air: If your radiator is warm at the bottom but cold at the top, it’s likely air is stuck in the radiator.
2. Secret sludge build-up: If the radiator is cold at the bottom and warm at the top, there could be a build-up of sludge or debris blocking the hot water flow.
3. System pressure issues: Low boiler pressure can stop radiators from working properly.
4. Valve problems: Stuck or faulty thermostatic radiator valves (TRVs) can prevent heat from circulating.

Bleeding your radiator: Save money with this easy fix

If your radiator is cold at the top or making gurgling noises, bleeding it could solve the problem in minutes.

Industry data shows** that the average UK cost of hiring a professional to bleed your radiators ranges from £80 to £100 for 5-10 radiators (taking 1–2 hours) or £100 to £150 for 10–15 radiators (taking 2–3 hours).

However, Gill advises that this is usually a relatively simple job that many homeowners will be able to competently undertake themselves.

“By learning how to do it yourself, you could pocket that cash instead of paying for a professional - and it’s a lot easier than you might think!”

“If you get stuck or simply would rather have the reassurance of a professional engineer, at BOXT we charge a flat callout fee of £89 for a one hour consultation visit - which includes services like bleeding radiators - so you should never be paying £150.”

Here’s how to do it:

1. Turn off the heating.
2. Find the bleed valve. This is usually at the top right or left of the radiator and looks like a small square or a slot for a screwdriver.
3. Prepare your tools. You’re going to need a radiator key or flathead screwdriver and a cloth or small container to catch any water.
4. Release the air. Turn the valve anti-clockwise slowly until you hear a hissing sound—this is the trapped air escaping. Keep the cloth handy to catch any drips.
5. Close the valve. Once water starts leaking steadily, retighten the valve.
6. Check the boiler pressure. Bleeding radiators can lower the system pressure, so top it up to between 1-2 bars if needed.

Avoid these common mistakes:

A key step is letting your radiators cool completely after turning off the heating before you start bleeding them.

“Skipping this could result in scalding hot water spraying out or air being drawn into the system. While it’s fine to turn on your heating briefly to identify which radiators need attention, make sure they’re entirely cool before getting started.” adds Gill.

Also don’t skip bleeding your radiators just because they seem to work. “You should bleed your radiators twice a year, even if they’re functioning well.”

Why is my radiator cold at the bottom?

A radiator that’s warm at the top but cold at the bottom is often a sign of hidden sludge build-up.

Over time, rust, limescale, and debris collect at the bottom of radiators, making them less efficient and costly to run.

“A radiator clogged with sludge can’t heat your home efficiently. This forces you to keep the heating on for longer, driving up energy costs.” Gill explains.

The average annual energy bill in England, Scotland, and Wales rose to £1,738 in January 2025, as the price cap increased by 1.2%, adding more pressure on household finances.

Regularly flushing central heating systems can help cut bills.

Removing sludge can improve radiator heat output by up to 47%, as well as reduce gas usage and carbon emissions by up to 7%, and even extend the life of a boiler by up to 7 years.

Gill adds: “By clearing any blockages in your heating system, radiators can heat your home faster and more effectively, meaning you’ll rely less on keeping the heating on for extended periods.”

Here’s how to tackle it:

1. Turn off the heating and let it cool. Safety first.
2. Protect your flooring. Place towels or old sheets around the radiator to catch any mess.
3. Turn off the radiator valves at each end of the radiator
4. Drain the radiator. Crack open the nut on the radiator side of one of the radiator valves or TRVs to release water into a container.
5. Once water stops flowing remove the radiator from the valves and wall brackets, turn it upside down to transport it to a foul waste drain.
6. Open the bleed valve on the radiator and use a hose pipe to flush the radiator out from one of the open ends into the drain.
7. Once clear, replace the radiator and tighten the joints, open the radiator valves ensuring no leaks and tighten the bleed valve. Then top up the system pressure and bleed the radiator.
8. Switch heating back on. Test the results.

NB: Only attempt this if you are confident in your DIY skills. Bigger blockages will require a system flush by a professional

If the issue persists, a professional power flush may be necessary. Gill recommends “a MagnaCleanse over any other type of flush. Approved by our manufacturer partners - it’s a highly effective way of keeping your system protected. This procedure should always be carried out by a Gas Safe engineer.”

Avoid these common mistakes:

1. Tightening the bleed valve too much: when bleeding your radiator, don’t overdo it when closing the valve. Tighten it just enough to stop water from leaking - overtightening could cause damage or future leaks.
2. Forcing stuck valves: if a valve is stuck, don’t force it open. Try gently tapping it to loosen it or get professional help if it won’t budge.
3. How to check your boiler pressure: low boiler pressure can also stop your radiators from heating up properly.

Here’s how to check:

1. Locate the pressure gauge. This is usually on the front of your boiler.
2. Check the reading. The needle should sit between 1-1.5 bars when the system is cold.
3. Top up the pressure. If it’s too low, use the filling loop, filling key or filling link (refer to your boiler manual to find out which you have) to add water. Don’t overfill - too much pressure can damage the system.

Gill adds “Taking a little time to learn the basics of radiator and boiler care can make a big difference - not just for your wallet but also for the efficiency and lifespan of your heating system.

“Simple steps like bleeding radiators, flushing out sludge, or checking boiler pressure can help you avoid costly issues and keep your system running smoothly.”

“You’ll save money and gain the confidence to handle minor problems before they escalate. If you’ve done all the above and your radiator still isn’t firing up, don’t hesitate to contact BOXT. Whether it’s a quick question or a more complex problem, our team of in-house engineers is here to help.”

For more information go to BOXT.co.uk