Power Flushing: How to Price and Sell It

Cold spots at the bottom of radiators. A boiler that locks out for no obvious reason. Black sludge on the water when you bleed a rad. You know exactly what the system needs — a power flush — but pricing it and getting the customer to say yes is where a lot of heating engineers come unstuck. Quote too low and you wreck your margin on a labour-heavy job. Quote too high without explaining the value and the customer thinks you're trying it on.

This guide walks through how to price a power flush properly, how to sell it without sounding like a salesman, and how to protect your day rate while you're at it.

What you're actually selling

A power flush isn't a magic cure-all, and it pays to be honest about that from the start. You're using a pumping unit and a chemical cleanse to shift the magnetite sludge, rust and debris that builds up in a heating system over years. Done right, it restores circulation, gets radiators heating evenly again, quietens a noisy boiler and protects the heat exchanger.

What it won't do is fix a system that's mechanically failing for other reasons. Set that expectation honestly and you'll never get the "but you said it would fix everything" call back. Customers respect a tradesperson who tells them the limits.

The job typically involves:

• Connecting a power-flushing machine to the system
• Running a chemical cleanser through each circuit and radiator
• Agitating and reversing flow to dislodge stubborn sludge
• Flushing through with clean water until it runs clear
• Dosing with a corrosion inhibitor at the end
• Often fitting a magnetic system filter to keep it clean

That last point matters. A flush plus a filter is a far stronger sell than a flush alone, because the filter protects the work you've just done.

How to price a power flush

There's no single right number — it depends on the system, your area and how you run your business. As a rough guide, a domestic power flush in the UK often lands somewhere in the region of £300 to £600 plus VAT, with larger or heavily sludged systems pushing higher. Don't treat anyone's published figure as gospel; price your job.

The honest way to price it is bottom-up, from your own costs:

1. Count the radiators. More rads means more time, more chemical and more flushing. Price per radiator or band it (e.g. up to 8 rads, 9–12, 13+).
2. Cost the time. A typical domestic flush is the better part of a day. If you don't know your true day rate, sort that first — our guide on how to calculate your hourly rate is the place to start.
3. Add materials. Cleanser, inhibitor, the magnetic filter if you're fitting one, plus wear on your machine.
4. Factor in access and condition. An old system in a hard-water area with seized valves takes longer. Build in a contingency rather than eating the overrun.
5. Apply your markup on materials. Don't sell the filter and chemicals at cost — see material markup: how much should you add?.

Quick tip: price the flush and the magnetic filter as one "system protection" package rather than two line items. It's easier to sell, the customer sees one clear outcome, and it nudges your average job value up without feeling like an upsell.

Fixed price or day rate?

Most customers want a fixed price for a flush — they want certainty, and a single number is easier to say yes to. But you carry the risk if it overruns. The trick is to scope properly first: count the rads, check the system condition, and price for the system in front of you, not a textbook average. If you're weighing the trade-offs more generally, day rate vs price work breaks down where each wins.

How to sell it without the hard sell

The best way to sell a power flush is to not sell it at all — diagnose it. Show, don't tell.

• Use evidence. A thermal image of a cold radiator, or simply letting the customer feel the cold bottom of a rad against a hot top, makes the problem real. Black water in a jam jar tells the story better than any sales pitch.
• Explain the cost of doing nothing. Sludge doesn't get better on its own. Left alone it can cost a pump, a heat exchanger, or eventually the boiler. A flush is cheap next to a new boiler.
• Tie it to what they care about. Lower bills, warmer rooms, a quieter boiler, fewer breakdowns. Customers don't buy "power flushing" — they buy a warm house and peace of mind.
• Offer the protection upgrade. Fitting a magnetic filter and dosing inhibitor keeps the system clean for years. It's an easy yes once they've seen the sludge.

Be straight about when a flush isn't the answer. If the system's beyond it, say so. Turning down a flush you don't believe in earns more trust — and more future work — than taking the money.

Get the quote out fast

Diagnosis and pitch mean nothing if the written quote lands two days later. By then the urgency's gone and they've rung someone else. The job you've already half-sold on the doorstep is lost to a slower follow-up — which is exactly the trap covered in why you are losing jobs to slow quotes.

This is where a job-management system earns its keep. With Gaffer you can build the quote on site from a power-flush template, send it before you've left the drive, and have it accepted on the customer's phone while the cold radiator is still fresh in their mind. Less admin in the van, faster yeses, fewer jobs lost to delay.

Protect your margin and get paid

A power flush is labour-heavy, so margin leaks hurt. Two things protect it:

• Take a deposit on larger jobs. It commits the customer and helps your cash flow. Deposits and staged payments covers how to structure this fairly.
• Invoice on the day and make paying easy. Don't let a same-day cash job drift into a chased debt. Send the invoice before you pack up the machine.

Automated payment reminders mean you're not the one chasing — Gaffer nudges the customer politely until it's paid, so a flush you finished on Tuesday doesn't still be outstanding three weeks later. If late payment is a recurring headache, how to get paid faster has the full system.

Turn one flush into a relationship

A power flush is a perfect doorway to repeat work. You're already in the home, you've earned trust by being straight, and you've left them with a cleaner system. Suggest an annual inhibitor check or fold it into a service plan, and a one-off becomes a customer you keep. The filter you fitted needs cleaning periodically too — that's a natural reason to come back.

Price it properly, diagnose rather than sell, protect your margin, and a power flush stops being an awkward upsell and becomes one of the most profitable jobs in your week.

FAQs

How much does a power flush cost in the UK?

As a rough guide, a domestic power flush often falls somewhere around £300 to £600 plus VAT, depending on the number of radiators, system condition and your area. Larger or heavily sludged systems cost more, so always price the specific job rather than quoting a flat figure.

How long does a power flush take?

A typical domestic power flush takes the better part of a day — often four to six hours, though older or larger systems with stubborn sludge can take longer. Always allow contingency for seized valves and poor access.

Is a power flush worth it?

If a system has uneven radiator heating, cold spots, noisy boiler operation or visible sludge, a flush usually pays for itself by restoring efficiency and protecting expensive components like the heat exchanger. If the system is mechanically failing for other reasons, be honest that a flush won't fix it.

Should I fit a magnetic filter after a power flush?

Fitting a magnetic system filter and dosing a corrosion inhibitor is strongly recommended, as it captures debris and protects the freshly cleaned system for years. Selling the flush and filter together as one protection package is both easier for the customer and better for your average job value.