Welcome to Quotation Check – Your guide to home improvement costs in the UK. How much does it cost to power flush a central heating system? We have been researching tradesman’s prices and charges for nearly three years, so explore our findings and hopefully, we can save you money too.
What is Quotation Check and Where Did These Prices Come From
The prices you see displayed on this page are based on written quotations supplied by plumbers and heating engineers in the United Kingdom.
Our hope is that you can avoid traders who overcharge and budget your finances accordingly.
Don’t forget that every project is different and the quotes we gather may be different to the ones you source. If you need a firm price, we suggest you contact three local plumbers and compare prices yourself. See exactly how we gather quotes from tradespeople here.
We launched our website in 2014 and since then, we have grown to become one of the most popular home improvement price comparison sites in the UK.
We think our research is insightful and a great starting point for those investigating trade prices.
How Many Heating Engineers Provided Quotes?
We sent out 21 quote requests but only 17 responded and provided us with quotes for the work.
The chart below shows all the figures we received, this includes both one-man type tradespeople and also larger companies;
Power flushing is a technique used to clear out sludge from central heating system pipes, radiators, coils and heat exchangers. These are areas where scale and corrosion can collect; the symptoms are usually:
- Cold spots on radiators, even after bleeding
- Takes a long time for radiators to warm up
- Noisy boiler
- Radiators needing regular bleeding
- Inefficient central heating system
Once a power flush is complete, you can expect the following benefits:
- Pipes and radiators will get hotter quicker
- More cost efficient system
- Less stress on the boiler
- Increased life of the boiler
- Heat will be distributed more evenly throughout the home
Central heating boilers can fail early if there is excessive sludge in the system, modern condensing boilers are much more sensitive, so it’s recommended to have a full system flush before installing a new boiler. There is no point in paying for an expensive piece of kit that may fail early because of excessive sludge build up in the system!
You should also check the guarantee on any new boiler as most manufacturers will not accept a claim if the system hasn’t been recently power flushed.
Checklist for Power Flushing Radiators/Central Heating System
- Record temperature of radiators (so we know which are heavily clogged)
- Record TRV settings on each radiator
- Take water sample
- Open all valves and remove TRVs
- Bridge any valves or equipment that may prevent reverse flow, i.e., pump
- Isolate boiler
- Take precautions to protect carpets etc
- Connect power flushing unit
- Carry out primary and secondary flushes dislodge stubborn sludge with rubber mallet or vibrating tool
- Remove any stubborn radiators and manually clean with a hose. Refit rads.
- Take temperature of individual rads and compare to original radiators
- Test water
- Add inhibitor (also neutralizer depending on system) and test
- Reinstall TRV’s and any other valves and apply original settings
Cost to Power Flush Central Heating Radiators and Pipes
How much does it cost to power flush a heating system? What is a fair price to pay and will you save money in the long-term?
It wasn’t difficult to gather a large pool of quotes from various plumbers and heating engineers up and down the country, many of our chosen businesses were happy to provide a price/cost without visiting the property, some such as British Gas insisted on a visit.
Gas engineers usually advise homeowners to have this work carried out when installing a new boiler or if the homeowner hasn’t cleaned the system for a long time. Once complete, the system should run more efficiently, saving you money. Although it is impossible for us to predict a return on your investment.
Our quotes were all for 2-bed houses with a boiler less than 20 years old.
As you can see from our table below, the average cost of a power flush is £470.00.
|Location||Small Business /Trader||Larger Business (5+ employees)|
|Need a Custom Price? >|
|South, SW and Midlands||£425.00||£525.00|
|Outer Region and North||£350.00||£500.00|
(the table above was last updated 17th February 2017)
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What You Get For Your Money – How Power Flushing Works
During the initial consultation, your chosen contractor should explain the work involved and the expected cost savings.
Before commencing with the actual work, your tradesperson should start the boiler and check all the radiators for cold spots, ideally taking the temperature of each rad. A sample of the water should also be taken for comparison.
Once all radiator valves have been removed or opened, dust sheets placed over carpets, etc., this, the power flushing machine can be connected. The first flush will involve a chemical power flush of the entire system including a reverse circulation; this usually takes around 20 minutes. Each rad is then isolated and flushed, starting with the coldest rads. A rubber mallet can be used to loosen up any scale/sludge. The tradesperson will then duplicate this process across all the radiators.
A second flush takes place across all radiators individually; the fluid is reversed periodically until the water is clear and free from sludge. This is repeated with all radiators.
A final full system flush is then undertaken, this is continued until the water being dumped is clear and free of sludge.
Finally, an inhibitor is added to the water and circulated through the system for 15 minutes. A sample is then taken and tested; more inhibitor can be added if required. The TRVs (radiator valves are then refitted and set to their original settings)
How Long Does it Take?
The length of time it takes to flush the radiators depends on how many there are and also how much sludge is inside them.
For a typical two bed house assume a timeframe of 4-6 hours.
If your tradesperson has to remove lots of radiators, manually flush each one with a power washer and then refit them, assume it will take longer.
Q: Do radiators need to be removed?
A: In some cases, compacted sludge can only be removed by removing the rads and manually cleaning them with a powered pressure washer/hose.
Q: Instead of having the system flushed can I not just install a permanent magnetic filter?
A: Sludge caught in the rads will not circulate so won’t be captured in a magnetic filter unless a power flush is completed. These filters only catch loose sludge, not sludge which is compacted.
Q: I have had my rads repeatedly flushed, but they keep blocking up with sludge, what gives?
A: If your heating system is allowing oxygen into the pipework, this will accelerate the corrosion of the pipes/rads leading to frequent and excess development of rustic sludge. We suggest you have your heating system checked by a qualified engineer before you flush the system again.
Q: How often should I have the system power flushed
A: If done correctly you shouldn’t need to have the system flushed for 10+ years, but if the rads/pipework are corroding and producing fresh sludge then it need to be flushed sooner. Having the correct levels of inhibitor in the system and having this checked/topped up yearly will help. Make sure you make a note of which brand of inhibitor has been used, otherwise testing will be inconclusive (some installers leave the empty bottle behind)
Q: Can all types of central heating systems be flushed?
A: Yes, all types of heating systems can be flushed.
Q: Are TRV (rad valves) an issue?
A: No, the pins can get stuck as a result of the sludge, but this is easily checked and remedied.
Q: I have received a quote for £150, is this a fair price/cost?
A: For this price, we would not expect a complete and thorough power flush, although water may run clear after a power flush it may be because the water is flowing over compacted sludge. Removing this compacted material takes time as it often involves tapping the rads or removing them and manually cleaning them. We would suggest £300-£450 for a two-bed house as a guide price, depending on location. Prices do vary. Obviously, some smaller firms may charge below £300 while large companies like British Gas have been known to charge well above £600.
Q: Should I have the central heating system drained and refilled every year?
A: No. This will only add oxygen and other impurities to the water; this will accelerate the corrosion.
Q: What is the sludge made from?
A: It is mostly rust that corrodes from the metal pipes and radiators, but also contains contaminants from the water.
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