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The Powerflushing Method

The powerflushing process is made up of several separate processes, which for an average sized domestic heating system (approx. 7-9 radiators, between 10-20 years old), takes on average around 7-8 hours to complete, including re-instating the system, re-balancing and testing operation on completion. The process is outlined below..

System Preparation

A traditional open vented system is fed by a tank, which both feeds the system and lets it expand via cold feed and open vent pipe work. These pipes therefore are 'open ended' and have to be disconnected and capped throughout the powerflushing process. Therefore the tank is isolated, drained, and this pipe work temporarily capped. The complete system also needs to be electrically isolated to prevent the boiler from firing and causing potential catastrophic damage!

The powerflush machine is best set up outside if possible, but this will depend on a suitable drain being nearby, along with a suitable connection point to the system, within reach of the hoses. Excessively long runs of hoses are avoided as this can increase restriction and the time for returning water to get back.

The powerflush machine is connected to the system by means of two 22mm hoses. These hoses become 'flow and return' pipe work with the system and the machine itself effectively becomes the pump of the system. The point at which the machine is connected to the system is very important. This is usually in place of the existing pump, so this has to be isolated, drained and electrically isolated.

If the system also heats the hot water (as most do), there will be a path the water can take to this circuit. This needs to be isolated by means of temporarily closing this hot water port, for example - a 3 port valve will need to be motored over to the heating only position. This is imperative, as any bypassing of the system water down circuits you don't want it not only contaminates areas that have already been cleaned later on, but more importantly vastly reduces flow rate to the circuit you are wishing to clean, and therefore how effectively it's cleaned. All this also goes for removing bypasses etc.

Initial cold flush

With the powerflush machine and system now connected, the machine is connected to a water supply and the machine is set up to pump fresh water into the system (with all radiators and balancing valves fully open), and returning fouled water is diverted via a 22mm hose pipe to drain. This is done reversing the flow through the system to initially loosen any deposits.

It is then carried out with single individual circuits open, until water runs clear in each circuit.

Hot Chemical Flush

A chemical is now added to the system via the machine, which reacts with the magnetite and solid build up, and loosens it from the surfaces within the system. This is run with the complete system open so that it makes it's way into the whole system. The flow is reversed several times during this period. If the boiler is still in use, it is run to heat the water, as the chemical works far better with heat. Most machines can only operate at around 40 degrees Celsius, but ours can operate at 80 degrees Celsius. If the boiler cannot be operated, our machine has a built in heater which brings the water up to 60 degrees Celsius, unlike most other units.

Next, each section of the system is closed bar one, so that the full flow rate is concentrated in one area. Once again, the flow is reversed throughout this period to help dislodge stubborn deposits. This is repeated for every radiator/circuit of the system. The temperature of each radiator is used to determine where areas of solid sludge build up are (the middle/bottom of radiators), and these are concentrated on. By use of a rubber mallet, these areas are shocked to further loosen, and regain flow. The diagram below shows how the build up effects flow.

This part of the powerflushing process takes around 10 minutes per circuit (radiator etc). But is governed by the severity of corrosion within the system.

Secondary Cold Flush

Next, the powerflush unit is emptied of the circulating fouled water and flushed clean with fresh water. Then, section by section, individual circuits (radiators etc), have fresh water pumped into them, pushing the fouled water/deposits back to the machine, which is then diverted out to the dump hose and out to drain. The flow is reversed several times on each circuit until they run clear on reversal. This is usually the longest process and can easily take 15 minutes per circuit to run consistently clear. Many times, badly fouled radiators (or complete systems), can take up to an hour per radiator, during this part of the process. Needless to say, the benefits of this particular part of the flush, are huge.

Here's some stage picture examples of fouled water clearing on return to drain.

Final Cold Flush

Finally, all system circuits are fully opened again and the complete system flushed again. Any residual fouling in pathways that have been isolated and moved on to the next, during the previous flush, are cleaned again. The water commonly runs a straw colour during this flush, and the reversing process is repeated again until the water consistently runs clear.

Cleaning The Cold Feed and Expansion Tank

At this point the tank is removed and cleaned of fouled water and debris. A common problem is bacterial contamination of the tank, which unless chemically treated will return as growths again. This can also be treated by us and we will advise if it is required.

Re-Instating The System

The tank is then re-instated to the system. The powerflush unit is disconnected and all components re-instated. The system is re-filled adding a corrosion inhibitor chemical and vented. The system is then fully balanced and tested.

The process is complete.

Is Your System Too Big For The Powerflushing Process?

No. Our powerflushing unit is capable of flushing systems in excess of 20 radiators. For larger systems the process is carried out systematically to achieve the same results. Similarly, no system is too small, below is an average cost. Contact us for a specific quote on other size systems.

How Much Does It Cost?

We carry out comprehensive full system powerflushes involving all of the above, on a typical 3 bedroom domestic property from as little as £400.00, including all powerflushing cleaning chemicals and corrosion inhibitor chemicals. Please contact us on 01702 741789 (office), 07968 943447 (mobile) or Email, for free advice/quotes specific to your system requirements.


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