Power flushing is a more efficient and quicker way of cleaning a central heating system. It consists of flushing through all the system using water (and usually a cleaning agent) at high velocity, but low pressure, so that no physical damage is caused to the system. When installing new boilers in old central heating system it is important that all sludge is first removed from the system as it could accumulate in the new boiler.


Central heating system problems – poor circulation, boiler noises?

In hard water areas old systems will have accumulated lime scale and corrosion deposits, which can affect the efficiency of the boiler. Power flushing will break up hardened deposits allowing them to be flushed away easily. This will then restore central heating systems to optimum efficiency.


How we powerflush an existing central heating system.

There are a number of ways that we can connect our equipment to the system in order to carry out the powerflush; one method is to connect to the flow and return valves on a radiator. Another is to isolate and remove the central heating pump and the flushing unit connected between the pump valves. The unit has its own powerful pump. We add a cleaning solution and flush through the system.


The following are some of the questions we’ve been asked regarding powerflushing:


How long does it take to power flush a system thoroughly?

It will vary from house to house, but will take a little longer with a vented heating system than it would with a sealed or combi system.


How big a heating system can you do?

The largest that can be powerflushed at any time will be up to 12 radiators. Any system larger than that will require powerflushing to be done in sections. This generally means just shutting off radiators to reduce the size temporarily.


Would you need to drain down the system before you start?

No, we only need to run some water out of the system to lower the water level in the feed and expansion tank, so that we can cap it off.


Can you over pressurise a system, and blow joints?

No, the unit we use has a centrifugal type pump. What it can’t push through a system, it will simply re-circulate in the tank. Maximum pressure is less than two bars.


Can you power flush a microbore system?

Most certainly, but the connection will be made on to the circulator pump fittings, and not on to a radiator, otherwise the small bore tubing will drastically reduce the flow rate, and the system power flush will be less successful than normal.


Can you power flush a system with plastic piping, such as Hep2O or underfloor heating?

Most certainly we can. We use the recommended type of liquid specifically designed for this purpose which is used on plastic pipework systems, and will not damage either the pipework, or the ‘O’ ring materials.


Will power flushing cause damage to a heating system?

It is rare for a heating system to experience leaks after the power flushing process. However, the following must be given due consideration prior to commencement of any powerflushing:

i) Sludge and debris are present as a result of corrosion over a long period of time.

ii) The power flushing process will cure most circulation problems, but cannot undo the corrosion and gradual decay of heating system components that has led to the need to power flush the system.

iii) Occasionally some systems may have radiators with localised deep corrosion pits, with only a scab of rust preventing the system water from leaking out. The vigorous flow rate required to mobilise sludge and deposits may dislodge such a scab, leading to a leak from the radiator during the flushing process.

iv) The advanced stage of corrosion required for such a situation means that the leak would occur imminently even without a power flush. If it should be brought forward slightly by the flushing process, then it is better that it occurs whilst a heating engineer is present to remedy the problem, rather than for it to arise over a weekend or whilst the house is unoccupied.

v) Generally, power flushing chemicals are comprehensively inhibited, so that they do not affect the metals from which heating systems are constructed. They are formulated so that they loosen and dissolve the corrosion products that cause boiler noise and circulation problems, enabling the power flushing process to power them out of the heating system.


It is important after the flushing process to add a good quality inhibitor to the heating system to prevent future decay. Building Regulations Part L: 2006 now make the addition of a chemical corrosion inhibitor mandatory.


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