How to do a DIY power flush on your sealed central heating system

First you need to know which system you have; sealed systems have a pressure gauge on the boiler while open vented systems have a f&e water tank in the loft. If you don't have a pressure gauge, but do have the tank it the loft switch to the DIY guide for power flushing open vented systems.

(At no point will we take any liability for your actions when using this guide or any of the information provided by us. If you don't know what you are doing - Get a professional in)

We are assuming that you have sufficient knowledge to understand the working of the central heating system and the boiler. Your plumbing skills should at the very least be up to connecting and disconnecting a radiator from the system. This is not the professional "how to" version, but it will work well for systems that are currently working fine with no problems or faults on them. If your system has a problem – use a professional like one of our local members it's more affordable than you think. The biggest problem with doing a DIY power flush is that you don't have a "proof of power flush" when you are finished; it is a certificate issued by professional power flush companies showing that the power flush was completed and to a professional standard. Insurance companies tend to ask for these, before they are willing to carry out any further work on your system. If you don't have a proof of power flush, they are likely to refuse work and future cover.

NEVER USE ACID to do the power flush, leave that to the experts. A power flush machine has a flow rate of around 100liters per minute, so it can fill your bath in one minute - if you are unsure about what you are doing it might be better to let a professional handle it. We aim to explain how to use a power flush machine correctly.

Rent a machine and buy 2 chemicals (1 sludge remover and 1 central heating inhibitor)

1) Drain radiator: Bathroom radiator is best because you have a water supply, toilet to drain dirty water down and a water proof floor. Close both taps on the radiator – left and right. Have some cloths / towels ready. Loosen (not disconnect) one of the nuts that connecting the radiator tap to the radiator. You will need to be patient and have a flat dish or try to catch the water in as the radiator drains down; this takes 2-15min depending on radiator size. The water is normally black or brown on dirty systems.

2) Connect machine: When you are sure that all the water has been drained out. Disconnect both left and right radiator taps from the radiator and lift the radiator out. Putting it in the bath (if you have one) is normally best. Now connect the two hoses that come from the power flush machine to the two radiator taps – you should be supplied with adaptors. Now open the two valves of the bathroom radiator – you are now connected into the system. The water level in your machine will rise even overflow as the pressurized system backflows into your machine. Terminate the dump hose in toilet, taping it down is a good idea.

3) Filling machine: put the power flush machine in the bath or shower tray and connect the flow, return and dump hoses to it (read machine instructions). Most bathrooms have shower head connected to a flexible silver hose, disconnect the showerhead and use hose to fill machine. Be careful not to overfill, if it’s not in a bath or shower tray.

4) Open radiators: Go to all the radiators and open both left and right valve to full – turn all the way left.

5) Starting up: Plug in and start the machine – note the direction of flow can be changed by flipping a switch or turning a valve (read instructions)

6) Start the boiler by turning the temperature up to 30 degrees and putting programmer to constant. The whole system should heat up including the water in your machine. Note: some boilers will not work when the pressure is too low, so there is a chance that you cannot get the boiler to run while flushing.

7) Now add the “sludge remover” chemical and leave it in with the machine running for as long as it says on the back of the container – normally 2 hours. Supervise machine at all times; turn if off if you leave the room.

8) Isolate all radiators but 1: Turn off one valve on all of the radiators but 1 (the one you want to clean first) All of the flow is now concentrated through this one radiator. If you have a rubber hammer you can hammer the radiator to loosen sludge (bottom 20cm is best all the way along) Wait 5min then reverse the flow on the machine.

9) Fill and drain: Make sure the dump hose is terminated in the toilet. You now have to discharge the dirty water by opening the “dump” valve. Open it, you will see the dirty water coming out in the toilet. As you dump the water level in the machine will drop, you will need to fill it back up every time you dump. Try dumping a lot of water then filling with a lot. Do this until the water is as clean as tap water, then move on to the next radiator by opening the one closed tap on the next radiator before closing the one on the radiator you just flushed.

10) Cleaning the magnets: Stop the machine after every radiator is cleaned. Take the magnet/s out and wipe clean, they will have loads of black sludge if your system is dirty.

11) Move trough system one radiator at a time: reversing flow, dumping water till clean and cleaning magnets. Till they are all done, once the last radiator’s water is “tap water” clean. Now add the “inhibitor” into the machine and leave it running for 10minutes. You can turn the machine off, close the bathroom radiator taps and disconnect hoses and machine.

12) Wash bathroom radiator internally by filling and draining it using the flexible silver hose you used to fill the machine with (put radiator in bath). Once clean reconnect radiator, open both taps and bleed air out.



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