Central Heating Power Flush
A “Power Flush” or “Chemical Flush” of a Central Heating System assists in the efficient running of a boiler and central heating system. (Request a Quote)
This article explains, in layman’s terms:
- What is involved in a power flush.
- Why your central heating might need a power flush.
- What the symptoms are.
- What the cost of a power flush might be.
- Who is qualified to do a power flush.
What is a Power Flush?
- The process by which a build up of sludge composed of rust, scale, tiny metal particles and other debris is removed from the pipes, radiators and boiler that make up a central heating system.
- A machine is used to push a mixture of clean, mains water and chemicals through radiators and central heating pipes at high pressure.
- Usually it is done as a three step process – though can be more if there is a large accumulation of “sludge”
Why would a power flush be needed?
- Sludge is thicker than clean water. This means that it does not heat up as readily as clean water and cannot, as easily, be pumped around the radiators and pipe work of a central heating system.
- A power flush will replace the “sludge” with clean water
- The result is less strain on the boiler (in heating and pumping the water) making it less likely to break down and extending its life as well as reducing fuel bills. It also means that the central heating system will heat up faster.
How to tell if a central heating power flush is needed
- Tools are available to identify the need for a power flush. However, an experienced heating engineer can usually tell following a brief inspection.
- Some press reports suggest that British Gas engineers are incentivised to sell this service.
- Be aware that the symptoms may point to other faults in the system or boiler. Personal experience by the writer was of three Scottish Gas Engineers recommending a power flush when the issue was actually one to do with the ignition on the boiler.
- Symptoms can include:
- Certain rooms being colder than others.
- The system taking a long time to warm up.
- Radiators being cold at the bottom and warm at the top.
- Radiators requiring frequent bleeding.
- Increased boiler noise.
- A simple self-test would be to hold a magnet to the underside of any plastic or copper pipes. It the magnet sticks or feels “sticky” when pulled away there is likely to be a build up of sludge in the pipe. It’s then worth investigating further.
How often does it need to be done?
- “When it is needed” is the simple answer.
- With suitable filters and servicing it should be a very infrequent requirement.
- We found few websites suggesting every three years. To engineers we spoke to this seems excessive. Especially for a properly installed and maintained system.
- It is prudent – though not essential – to do a power flush when replacing a boiler.
- Some boiler manufacturers only validate warranties if a power flush is done when one of their boilers is installed in an existing central heating system.
What does it cost and how long does it take?
- “Time is Money” so the length of time it takes will directly affect the cost.
- The time it takes depends on the size of the central heating system (how many radiators there are) and how dirty the system is (How much sludge has built up).
- Any system will take at least half a day. It’s safest to reckon on your boiler being out of commission for a full day at the least.
- As a guide price a seven radiator house will cost in the region of £350 to £500 excluding VAT .
- In our experience British / Scottish Gas will almost always be more expensive than a local, independent heating engineer for exactly the same service.
- Beware of people offering to do it for £200. In our experience it won’t be a thorough job. Check the tradesperson’s qualifications (they should be Gas Safe Registered) before proceeding.
Any “words of warning”?
- During a power flush water is pumped round the central heating system at high pressure. It may inadvertently result in finding weak spots in pipe work and cause leaks. Leaks can often be sealed with a leak sealer.
- Sludge build up in pipes that is left untreated can go as hard as concrete. This makes a power flush less effective. It may also mean “Pre power flush treatments” are necessary. These use chemicals that are added to a system a week or two before the actual power flush. The chemicals loosen the hardened sludge making a power flush more effective.
- It’s possible to clear sludge using an additive in the system water rather than a power flush. The additive is allowed to circulate in the system for a couple of weeks. The system is then drained down and refilled with clean water. This can be cheaper though, arguably, less effective than a power flush.
- Regular, basic maintenance of your central heating system including boiler servicing, keeping the system water topped up with inhibitor and the fitting of a magnetic filter will greatly reduce the need for power flushing.