Power Flush Cost

Looking to find out how much a central heating power flush costs in the UK?

You can expect the cost of a power flush to be £400 in 2026 for a 6 radiator system. However, power flushing costs are dependent on a few factors.

So, what's included in this complete guide?

In this guide, we detail the typical cost of a power flush (including material and labour prices) so that you know what to expect before getting a quote.

We also identify the signs that your central heating needs power flushing or other types of attention to keep it in good working order.

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How Much Does a Power Flush Cost?

What is power flushing used for?

Power flushing is designed to clean out your central heating system by removing the sludge or debris that builds up over time.

How can this help your central heating system?

A lot of boiler and central heating problems come down to poor system water (sludge, rust and debris) building up in the pipework and components.

Power flushing can help to prevent boiler breakdowns and reduce maintenance costs, while at the same time making your heating system more efficient, saving money on fuel bills.

You’ll notice radiators heat up faster and more evenly afterwards too (especially if you’ve had cold spots for ages).

However, you shouldn’t attempt to carry out a power flush yourself. If it’s done incorrectly, it can cause considerable damage.

It’s usually recommended to have the system cleaned and flushed before a new boiler goes in, so you’re not fitting a shiny new boiler onto a dirty system. Depending on the condition, that might be a chemical flush or a full power flush. Either way, the system should be refilled and treated with inhibitor afterwards.

Power Flush vs Chemical Flush

A power flush and a chemical flush both clean a central heating system, but they are suited to different levels of contamination.

Power Flush

• ✔ A more intensive clean that uses a specialist machine to move water and cleaning chemicals through the heating system at high flow rates.
• ✔ Designed to shift built-up sludge and debris from pipework and radiators.
• ✖ Usually takes longer and costs more than a chemical flush.

Chemical Flush

• ✔ A gentler clean where the cleaning chemical is added to the system and circulated during normal operation.
• ✔ Often suitable for preventative maintenance and heating systems in generally good condition.
• ✖ May not be effective if sludge build-up is heavy or radiators have ongoing cold spots.

If sludge build-up is heavy or radiators continue to have cold spots, a power flush may be the better option. For heating systems in generally good condition, a chemical flush is often sufficient.

Early Signs That You May Need a Power Flush

A few early signs your system might benefit from a power flush include:

• Cold spots on radiators
• Noisy radiators or boiler pumps
• Slow heating radiators

However, it's good to note that these problems can also be caused by air in the system. But if you bleed a radiator and rusty brown (or near-black) water comes out, that’s a strong sign there’s corrosion and sludge in there. And it’s a good idea to get an engineer to check if a power flush (or another clean) is the right fix.

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Central Heating Flush Cost

So, how much is a power flush?

Let's take a look at the cost of a power flush for a heating system with a different number of radiators in the house.

For reference, a 3-bed semi-detached house typically has between 8 and 10 radiators, and a 4-bed detached house usually has between 10 and 15 radiators.

Power Flush Labour Costs

To give you a better understanding of the costs involved in a power flush, here's what you can expect to pay for labour, as well as the expected job duration:

Power Flush Supply Costs

Lastly, here are the supply costs involved with power flushing your system:

Additional Power Flush Costs

With a heating engineer already booked in, it makes sense to maximise their services to take advantage of any minimum call-out fees.

Here are some jobs and add-ons you can consider getting done at the same time, depending on your needs:

If You Want To Optimise Your Heating's Lifespan

Boiler Service Costs

A great job to do in tandem with a central heating flush is a boiler service.

Servicing your boiler will ensure it runs efficiently and correctly. Once your power flush is done, giving your boiler a fresh bill of health will mean it lasts longer without needing major maintenance over the years, other than regular servicing.

Boiler service costs are an average of £100 in the UK.

Radiator Bleeding Costs

Once your power flush has been completed, your heating engineer will need to bleed your radiators to eliminate any built-up air in your system.

Radiator bleeding costs £100, and will make sure all air has been removed to ensure your heating circulates correctly.

If You Want To Optimise Your Home's Energy Efficiency

Smart Thermostat Installation Costs

Adding a smart thermostat to automate your home's heating schedule can boost energy efficiency while reducing energy bills.

Smart thermostat installation costs start at around £265, and once fitted, you'll be able to control your home's heating from your smart devices, even when you're not in the house.

Other Work That May Be Recommended

Once your system’s been power flushed, fitting a magnetic filter (if you don’t already have one) helps catch future rust and debris before it causes trouble, which is a big help when it comes to protecting the boiler. Supply and installation is usually priced separately.

Is the build-up in the system really bad? A power flush can help, but it won’t fix every problem on its own. In some cases, a tradesperson may recommend extra steps — like targeted chemical treatment, manually clearing a problem radiator, or swapping out parts that are past saving.

Repairs and Small Replacements That Can Add to the Cost

• Replacing radiator valves (such as thermostatic radiator valves (TRVs) or lockshield valves) if they’re seized, leaking, or not controlling heat correctly.
• Fixing leaks at valves, joints, or older radiators if problems show up during or after the power flush.
• Clearing a single problem radiator if one unit is badly blocked and needs additional work beyond the standard flush.

Timing and Access Factors

• Weekend or out-of-hours appointments may have an additional cost compared to weekday slots.
• Parking, travel, or access issues can affect the final quote in some areas, especially if the heating engineer needs extra time to set up and move equipment.

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What's Involved in Power Flushing Work?

Power flushing is essentially a deep clean for your heating system. It’s done with a specialist machine that pushes water (and cleaner) through the pipes and radiators to dislodge sludge and debris.

Over time, the inside of steel radiators can corrode. That rust mixes with the system water, turns it dark, and settles in the bottom of radiators and pipework. That’s when you start getting poor flow, cold spots, and noisy heating.

Here’s what the process looks like when a heating engineer does it:

Before the Job Starts

• Quick system checks — The engineer will look for cold spots, noisy areas, and poor circulation, and take a brief look at the system water to see how dirty it is.
• Set-up and protection — Floors get covered, valves are set up for good flow, and the flushing machine is connected in the right place.

During the Job

• Cleaning flush — A cleaning chemical is run through the system, in both directions, to help break down the sludge.
• Radiator-by-radiator flush — Each radiator is flushed in turn (starting with the coldest), sometimes with gentle tapping to loosen stubborn build-up.

Radiators usually remain in place during a power flush. In rare cases, a tradesperson may remove a radiator temporarily if it is heavily blocked and cannot be cleared while connected.

After the Job

• Rinse, refill, and inhibitor — Once the water runs clear, the system is refilled, and a corrosion inhibitor is added to slow down future sludge build-up.
• Final checks — If needed, they’ll bleed radiators, check for leaks, and make sure everything’s heating evenly again.

Signs You Need a Power Flush

Central heating problems don’t always show up as a full breakdown. Most of the time, it’s little clues that keep cropping up. For instance, slow radiators, patchy heat, and odd noises.

Here are some of the most common signs that sludge could be causing trouble:

• Cold at the bottom of a radiator — The top warms up, but the lower half stays cool. That’s sludge settling in the bottom and restricting flow.
• Radiators still poor after bleeding — If you’ve bled them in the right way and they’re still patchy or slow, it’s more likely muck in the system than trapped air.
• Knocking, ticking, or gurgling — Noisy pipes and radiators can mean water isn’t moving freely because debris is getting in the way.
• Some rooms never feel warm — The heating’s on, the thermostat is set, but one or two radiators always lag behind. That points to poor circulation.
• Dirty water when you bleed a radiator — Rusty brown or near-black water is a strong sign there’s corrosion and sludge in the system.

Not sure what’s causing the issue?

Cold spots, slow-heating radiators, and strange noises can be caused by a number of issues, such as sludge, trapped air, or faulty valves. In some cases, a full power flush may not be the answer and it could be something much simpler and cheaper.

You can use MyJobQuote to find a local heating engineer who can assess the system, explain what might be causing the issue, and advise whether a power flush is required.

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Checklist: Hiring a Heating Engineer for a Power Flush

Power flushing isn’t a DIY-friendly job. It needs specialist kit, and if it’s done wrong, you can stir up more sludge, trigger leaks, or cause bigger issues.

So, if you’re getting quotes, here are a few quick things to check before you hire a heating engineer:

• Do they do power flushes regularly? Ask how often they carry them out, and what sort of systems they work on (older pipework, combi boilers, sealed systems, etc.).
• Can they explain what they think the issue is? A good engineer will talk you through whether it sounds like sludge, air, a stuck valve, or a pump problem before jumping straight to “flush”.
• Are they the right person for your system? If they’re working on a gas boiler, they should be Gas Safe registered. For other setups, they still need to be properly qualified for heating work.
• What’s actually included in the quote? Check it covers the cleaner or chemicals, the flush itself, inhibitor afterwards, and final checks (not just “power flush” as a vague line item).
• Will they protect your home while they work? It can get a bit messy. It’s fair to ask about dust sheets, how they’ll avoid spills, and what they’ll do if a radiator valve starts weeping afterwards.
• Do they have public liability insurance? It’s not a legal requirement, but it’s one of those things you’ll be glad they have if something leaks mid-job.
• Do they have reviews and proof of similar work? Look for feedback from other homeowners and, ideally, photos that show they’ve done jobs like yours before.

Not sure who to go with? Use MyJobQuote to find a local heating engineer. You’ll get free, no-obligation quotes from tradespeople near you.