The PowerFlush Association's recommended procedures and practices for power flushing in the UK:
1) Central heating systems should be kept sludge and debris free at all time, if you have not had a power flush done, you will need to have one done to prevent future breakdown/s or leaks.
We found that up to 80% of all problems related to your central heating and hot water are either directly or indirectly related to sludge / lime scale build-up.
2 ) It is recommended by the PowerFlush Association that when central heating water sample is taken,two samples of at least 250ml should be taken, after the boiler and pump has been running for at least 30min. The first sample can be discarded and the second used to form an opinion of the central heating water’s quality. (Picture)
3) It is recommended by the PowerFlush Association that acid for power flushing only be used by exception; 80% of systems today have rubbers, aluminium and other metals in them that will damage / leak if you use strong acids incorrectly.
A good example is the silver towel-rail radiators used in bathrooms, they are made from aluminium.
We recommend that sludge remover be used as standard practice, strong acids by exception and only by trained professionals.
4 ) The PowerFlush Association recommends leaving sludge remover in as long as possible before you do the power flush (do not exceed the manufacturer's instructions). If it is not practical to add it days or weeks before the flush, it can be added when power flushing the system.
Leave it in the system with the boiler running as long as practical and definitely more than the minimum time specified by the manufacturer.
5 ) The PowerFlush Association recommends that the power flush machine should be connected to any radiator, external pump or pipes. We recommend not to connect the power flush machine to the pump fitted inside the boiler, unless you are qualified, experienced and trained to do so. It is very risky as leaks and short-circuits can happen very quickly and easily. Also, depending on the size and strength of the machine being used, connecting through the boiler pump can damage the diverter valve and other parts of the boiler, depending on the boiler type and condition.
6 ) The PowerFlush Association recommends that inhibitor be added after the power flush has been completed and that the dosage be calculated to be 50% more than the manufacturer recommended, to compensate for small leaks and evaporation especially in open vented systems.
7) The PowerFlush Association recommends that when connecting a power flush machine through a radiator into the system, the connections should be made directly onto the pipe work and NOT through the radiator valves / TRV. We call this a full bore connection. (picture)
The radiator valves have narrow openings that act like strainers and prevent the cleaning out of larger sludge and debris pieces (picture) from the system, which can cause the procedure to fail even though all other recommendations have been followed.
8 ) If you need a power flush and the problem you are experiencing is intermittent or no hot water on a combi boiler, the PowerFlush Association recommends that besides a power flush of the central heating system, the secondary (plate) heat exchanger should be removed, flushed / descaled separately. We recommend that this procedure should be charged separately from the power flus0h as not everyone needs or wants it done. In some cases the person carrying out this procedure needs to be Gas Safe registered because of the boiler's layout. If you are NOT registered to work on gas; the simply way to avoid breaking the gas regulation, is to "never remove the boiler cover".
When in doubt use someone that is both a registered member of The PowerFlush Association and the Gas Safe Register (we include the registration number in the company profile of our members).
The main reason for the physical removal of this heat exchanger is that it has two separate parts; one for hot water and one is for heating water. The only way to see on which of the two sides the problem really is and which side to flush or descale, is by its physical removal.
Alternatively, the secondary heat exchanger can also be replaced instead of flushing it out. Note: this procedure is only for combi boilers, which has two heat exchangers as standard.
9) The PowerFlush Association recommends that professionals should use power flush machines with sufficient strength to clean at least 35 radiators, on all domestic jobs. This will speed up the process and make it more effective, especially on system sizes of over 10 radiators, were static head, resistance and drop of flow is a problem.
10) The PowerFlush Association recommends that magnets should be used in conjunction with cleaning chemicals to remove metallic debris from the system water, if the system water is going to be re-circulated. If you are dumping 100% of the returning system water a magnetic filter can be omitted.