Monday - friday
8.00AM - 6.00PM
  • 01494 452502
  • 079 4479 0261

about power-flushing

the importance of quality power-flushing

Disappointingly some heating engineers will assume that system contamination is the cause for poor heating performance without thoroughly investigating what the true cause may be, recommending powerflushing as a ‘cure-all’ solution which it definitely is not. We have been asked to powerflush heating systems, which have turned out to only require simple balancing, had we carried on and powerflushed the customer would have paid a great deal more than was necessary to no avail. Similarly powerflushing will not cure piping defects, or undersized pipework. 

Powerflushing plays an important part in restoring older heating systems. It is offfered by most heating companies these days, but not always for the right reasons and is often employed when inappropriate, or ineffective and sometimes when not necessary.

Some systems are not compatible with Powerflushing such as single pipe systems, some micro-bore systems and (unless significant piping modifications are made) semi-gravity systems, unfortunately, whether due to ignorance or unscrupulous selling we still see companies (some large enough to know better!) selling powerflushing on these types of systems. There are cleaning methods that can be be effective on these types of systems, although sometimes re-piping may be the best long term solution. If you have one of these systems we will be pleased to discuss thecleaning options.

A highly effective method

Having said all of the above, when employed correctlypowerflushing can be a very effective method of cleaning and restoring a central heating system. If a system has been in operation for 10 years or more, especially if open vented it may benefit from powerflushing, when a system has been in operation for 20 plus years, even if well installed and reasonably well maintained it is likely that powerflushing will remove considerable contaminants. Unless the system is one of the types mentioned above which are not compatible with powerflushing, we would always recommend it when a boiler is replaced.

Again this is true of many, if not most heating companies today, however the quality of the powerflush can vary greatly. Firstly the equipment employed may vary there are cheaper flushing machines on the market which do not have the power to handle larger or badly comtaminated systems, high volume is required, this is why we use a Kamco CF90 machine capable of handling even the largest domestic systems. In conjuction with this machine we use a Magnacleanse powerflushing filter, which incorporates two large magnetic filters capable of removing large quantities of magnetite from the system.

When considering which company to use to clean yourheating system, we suggest you ask them for their procedures and for details of their equipment and compare them to ours.

The second important factor is the method used. A thorough powerflush can be very time consuming and it is impossible to predict how long a flush will take before starting, as many factors will influence this, but there are certain procedures that should be followed to ensure a thorough power-flush. Many of these are overlooked by those keen to do a fast, rather than a thorough, job.

We use the following procedure:
  • Where boilers are being replaced, we alter piping first, but always flush before connecting the new boiler and circulating pump to ensure that these are not contaminated. Where boilers are remaining in place the boiler can be fired at low temperatures to aid the flush.
  • The flushing machine should be connected to the main flow and return piping, either in place of the circulating pump, or to the main boiler tails with the circulating pump removed, connection in place of a radiator should only be the last resort, as this is the least effective. in the case of a combi or system boiler the flushing machine is connected to the boiler mounting frame before hanging the boiler.
  • Before filling, all motorised valves, radiator valves and lockshields should be fully opened to ensure maximum flow.
  • After initial filling, the water returning to the machine is usually discoloured, the flushing machine should be filled with clean water and the return water dumped to drain until the return water is clean. This will ensure that the chemicals are most effective. The magnetic filters should be checked and cleaned at this point.
  • The water level in the machine should be reduced to the minimum level and cleaning chemical can now be added and circulated around the system for about 15 mins, to ensure it is well dissolved.
  • At this point every single radiator except the one to be cleaned should be isolated, the cylinder coil should be treated as a radiator and isolated until it is time for it to be flushed, any system by-pass valves must be fully closed.
  • Each radiator should be cleaned using forward and reverse flow from the machine to ensure any deposits are agitated and at this point a Vibraclean tool can be employed where appropriate to maximise the separation of dirt deposits.
  • Once all radiators and the cylinder coil have been flushed, the magnetic filters should be cleaned and then each radiator circuit must be rinsed by flushing with clean water, whilst dirty return water being dumped to drain. This continues until the return is completely clean. This process is critical, it is imperative that this continues until the return is clean and clear, with little or no visible desolved solids, this is the area where people are tempted to cut corners, water must be regularly sampled, just because it may look clear out of the end of the hose does not always mean that it is clean! For particularly dirty systems the magnetic filters may require cleaning a few times during this process. if mains water pressure and/or flow are poor this process can be time very time consuming as the flushing machine may pump the water through faster than the mains can replenish it. Again the less than scrupulous engineer can be tempted to short cut this process by balancing the flow rate of the machine to match the incoming mains water, this will drastically reduce the efficacy of the flush, as a high flow rate is required to lift debris from the system, the correct procedure is to re-circulate the machine and allow the mains to catch-up.
  • Once all radiators have been flushed and the return from each has been observed as clean, only then can the flush be considered complete and the corrosion inhibitor added, this entire process may take several hours, or for larger systems sometimes more than a day to complete.
  • The final item worth noting is is the quality of the cleaning and corrosion inhibiting chemicals used, we only use major branded 'Sentinel' chemicals, as recommended by Worcester Bosch. We do not use plumbers' merchants own brand chemicals to save a few pounds. We always attach the stickers from the chemical bottles to the boiler after flushing to prove what chemicals have been used and record the date they were used.

about us

Smith’s Heating Services Ltd is a family run, Gas Safe and Oftec registered business serving High Wycombe and surrounding areas.

We specialise in central heating systems and boiler installations, but also have wide knowledge and experience in most areas of plumbing. We are qualified and registered to work on Natural Gas, LPG and Oil. We are also qualified to install un-vented hot water systems and fully trained on UK Water regulations. We provide comprehensive advice, high-quality professional work and a personal service.

why choose us

Over 90% of our work comes from referrals! We don’t just want to fit a new boiler, we want to build a long-term relationship with customers and have many customers that have used us again when they have moved house.
  • heating & plumbing specialists
  • affordable prices
  • no hidden costs
  • Finance available (subject to status)

get in touch

Got a question or need help? Don’t hesitate to contact us directly and we will be happy to assist you.


7 Derehams Lane
High Wycombe HP10 9RH




01494 452502


079 4479 0261

emergency plumbing

Imagine you come home one day to discover that a blocked pipe has flooded your home. You’re going to need professional help quickly!

8.00am – 6.00 pm Monday to Friday

If you have an emergency outside of these times please call, or email and we will do our best to assist.

  • 01494 452502
  • 079 4479 0261