Power
Flushing
Sludge out, radiators hot top to bottom, and a filter and inhibitor to keep them that way. Central heating power flushing across Andover, Marlborough and Hungerford, with a fixed price before I start.
Flushing Services
A flush is priced by the number of radiators, so every one is a written quote after I have counted them and looked at the pipework. Nothing starts until you have that in writing.
Full Power Flush
A power-flushing pump connected to the system, every radiator flushed one at a time until the water runs clear, magnetite and sludge pumped out, then the whole lot refilled and dosed. Priced by the number of radiators: a 12-radiator house with chemicals is £785 + VAT.
What's Included:
- Each radiator flushed individually, reverse-flow
- Cleaning chemical circulated to lift the sludge
- Magnetite collected and taken away
- System refilled and dosed with inhibitor
- Every radiator checked hot top to bottom
- 12-month workmanship guarantee
Chemical Clean
For a lightly fouled system, or one with microbore or elderly pipework that should not be put under a pump. Cleaner goes in, circulates for a few days on the system's own pump, then the lot is drained, flushed through and refilled.
What's Included:
- Cleaner dosed and left to circulate
- Drained and flushed with mains water
- Refilled and dosed with inhibitor
- Return visit included
- Right answer where a power flush is too much
Magnetic Filter Fitted
A MagnaClean or Sentinel Vortex on the return, between the last radiator and the boiler, catching the magnetite before it reaches the heat exchanger and the pump. The single best thing after a flush.
What's Included:
- ADEY MagnaClean or Sentinel Vortex
- Fitted on the return with isolation valves
- Cleaned out at each annual check
- Filter, valves and fitting included
Inhibitor Top-Up and Water Test
System water tested for inhibitor level and dosed back up. BS 7593:2019 says check it every year and re-dose every five, and a boiler warranty usually depends on it.
What's Included:
- Inhibitor concentration tested
- Sentinel X100 dosed to the right level
- Magnetic filter cleaned while I am there
- Written note of what was found
Underfloor Heating Flush
Wet underfloor loops flushed one at a time through the manifold, with seized manifold valves and flow meters replaced where they no longer move. Priced per manifold once I have seen it.
What's Included:
- Each loop flushed separately
- Manifold valves and flow gauges checked
- Loops rebalanced after refilling
- Inhibitor dosed
Cold Radiator Diagnosis
Cold at the bottom is sludge. Cold at the top is air. One radiator cold and the rest fine is a valve or the balancing. Not every cold radiator needs a flush, and I will say so.
What's Included:
- Every radiator checked and bled
- Valves, TRVs and pump checked
- System balanced if that is all it needs
- Straight answer on whether to flush
How a Power Flush Is Done
Connect and Dose
The pump goes on in place of the circulator or across a radiator tail, cleaning chemical goes in, and the system runs warm to loosen the deposits.
One Radiator at a Time
Every other radiator is closed off and the flow reversed back and forth through the one being cleaned, with a rubber mallet on the panel to shift what has settled.
Dump to Drain
Dirty water is dumped to a drain and replaced with fresh until it runs clear at every radiator. The magnetite that comes out is collected, and there is usually a lot of it.
Refill and Protect
The system is refilled, dosed with inhibitor, bled and balanced, and every radiator is checked hot from top to bottom before I pack up.
Expert Power Flushing
Expert Power Flushing by Will Gaze
I do the wet side of heating: radiators, valves, pipework, pumps and the water inside them. Power flushing is where most of the cold-radiator calls I get end up, because on 22+ years of chalk-water systems the sludge is the usual culprit, not the boiler.
I am not Gas Safe or OFTEC registered and I do not touch gas or oil boilers. If a flush is needed before a new boiler, I clean the system and a registered engineer fits the boiler, and the two visits are booked together. What you get from me is a written fixed price, one plumber start to finish, and 12 months on the work.
Do You Actually Need One?
A power flush is a day of work and a few hundred pounds. Some cold radiators need it. Plenty do not.
Signs You Do
- Cold at the bottom, hot at the top: sludge settles low in the panel and blocks the flow across it.
- Black or brown water when bleeding: that is magnetite, and if it is in one radiator it is in the boiler too.
- A noisy pump or a kettling boiler: the pump is working through mud and the heat exchanger is coated.
- Radiators that never get properly hot: even with the boiler running flat out and the system bled.
- A new boiler going in: the manufacturer wants a clean system, and the warranty depends on it.
Signs You Do Not
- Cold at the top, hot at the bottom: that is air. Bleed it. If it keeps coming back there is a leak or a pump pulling air in, which is a different job.
- One radiator cold, the rest fine: a stuck thermostatic valve or a lockshield that needs opening, not a whole-system flush.
- Upstairs hot, downstairs cold (or the reverse): balancing. Ten minutes with a lockshield key, not a day with a pump.
- A system flushed a few years ago with a filter and inhibitor: clean the filter and test the inhibitor first. It is probably fine.
The cold radiator diagnosis visit above exists for exactly this. If it turns out you do need a flush, that visit comes off the price.
Flushing Service Areas
One plumber and a flushing pump in the van, working out of Wootton Rivers. Every town below is a short drive.
Andover and Test Valley
Down the A338 and A342 from Wootton Rivers
- Andover (SP10, SP11)
- Upper Clatford and the Wallops
- Stockbridge and Chilbolton (SO20)
Marlborough and Pewsey Vale
Older housing stock, older pipework, more sludge
- Marlborough and Ramsbury (SN8)
- Great Bedwyn and Burbage (SN8)
- Pewsey and Upavon (SN9)
- Tidworth and Ludgershall (SP9, SP11)
Hungerford and Lambourn Valley
The Kennet valley, over the Berkshire border
- Hungerford (RG17)
- Lambourn and Great Shefford
- Kintbury, Inkpen and Combe
- Chilton Foliat and Shalbourne
Booking a Flush
A flush is a full day, so it goes in the diary as one. Same-day or next-working-day for most jobs; emergency slots subject to availability. You get a named date when Will confirms the booking.
Heating Guides
What sludge is, how to tell it from air, and what a magnetic filter actually does.
Frequently Asked Questions
How do I know if my heating system needs a power flush?
The classic sign is radiators that are hot at the top and cold at the bottom, because that is where the sludge settles. Black or brown water when you bleed one, a pump that is noisier than it was, a boiler that bangs and kettles, and rooms that never quite warm up all point the same way. A radiator that is cold at the top just needs bleeding, and one cold radiator with the rest fine is usually a valve or the balancing, so I check before I recommend a flush.
How long does a power flush take?
Most houses are a day. Count on four to eight hours depending on how many radiators there are and how bad the sludge is, because each radiator is flushed on its own until the water runs clear rather than the system being rinsed as a whole. A chemical clean is two shorter visits a few days apart instead.
Can a power flush damage old radiators or pipework?
It does not create weak spots, but it can find ones that were already there, which is why I look at the system first. Very old radiators, microbore pipework and anything that has been leaking or patched get a chemical clean on the system's own pump instead of a machine. If a radiator is too far gone to be worth flushing I will tell you before we start, not after.
Do I need a power flush before a new boiler?
Almost always. Boiler manufacturers want a clean system, an inhibitor and usually a filter before they will honour the warranty, and BS 7593:2019 says the same. I do the flush, the filter and the inhibitor on the wet side. I am not Gas Safe or OFTEC registered, so the boiler itself is fitted by a registered engineer, and the two visits are booked together so the new boiler goes onto clean water on day one.
What stops the sludge coming back?
Three things, in order. Inhibitor in the water, which slows the corrosion that makes magnetite in the first place. A magnetic filter on the return, which catches what does form before it reaches the boiler. And an annual check of both, because inhibitor gets used up and a full filter stops working. Do those and a flushed system stays clean for many years.
Important Booking Information
Our professional booking system ensures seamless service delivery from first contact to job completion
Your Call Gets Answered
In Your PA answers the landline in office hours, so somebody picks up when Will is under a sink. They take your details and pass them straight through. Will is the one who quotes the job and turns up to do it.
Arrival Windows
We provide time windows rather than exact times to ensure quality work on each job. We'll keep you updated with a more precise ETA.
ServiceM8 System
Our professional job management system provides SMS updates, online booking, and digital job records for a seamless experience.
What Goes In, and Where It Comes From
Cleaning chemicals and inhibitor are Sentinel: X400 or X800 to lift the sludge, X100 to protect the system afterwards. Filters are ADEY MagnaClean or Sentinel Vortex, whichever suits the pipework. All of it comes through Plumbfix and Trade UK, so it is on the van rather than on order.
Nothing proprietary and nothing you cannot check. The filter has a make and model on it and the inhibitor level can be tested by anyone with a kit.
See all the brands I work with
Radiators Cold at the Bottom?
Free survey, radiators counted, and a written price for the flush before any work starts.