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Flushing Radiators heated by Baxi Combi 80e & 105e

Postby XPC465 » Sun Jul 20, 2008 1:26 pm

Hi! there,
As this is my first posting on this site, may I say nice to meet you all.

I am an elderly pensioner, who in their lifetime has carried out numerous diy tasks, including wall building, installing electrics in my large shed etc., which have all proved very successful.

However I now need the advice of you decent people, to flush my central heating radiator system.

Although the radiator system itself is very old, having been in the bungalow since I purchased it in 1984, the Baxi Combi boiler which now heats it, was fitted about 2 years ago, by a qualified corgi engineer. Being a Baxi Combi, it heats the water as it passes through the boiler, and there is no water tank in the attic. I do feel since it was fitted, that the gas bill has been rising quite a bit, and I am sure that the radiators do not function 100%. I would therefore like to flush and clean out the radiators, but to save any unnecessary cost, I would like to do this myself.

Would some kind person out there please give me a step by step procedure on how to carry out this task, and what to use, so that I will not make a mess of it, and I will know exactly what I am doing.

Many thanks to all who offer advice.
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Simply Build It

Postby htg engineer » Thu Jul 24, 2008 10:15 am

Firstly check the radiators valves are open, and try balancing the system to get the best performance from all radiators. Also think about replacing rad valves with TRV's to help reduce heating costs.

To flush the system, drain the system and check the colour of the water remove one radiator and check for any sludge build up etc. Add system cleanser can be bought from most DIY shops and not expensive.

Leave in the system for the recommended time (follow instructions on bottle) drain ths system and refill, 1 x cold and 2 x hot.
If the pipes drop from the loft to each radiator, you will need to remove and drain each rad individually. Refill system and add inhibitor.

If there was any sign of sludge, attach a hose to a drain point. As the combi fill is fitted to the return, you want a drain point on the flow beneath the boiler, turn off the isolation for the flow and return under the boiler, as the system cleanser should have cleaned the heat-ex - you don't want loose debri's getting back in the boiler. Turn off all but one radiator and turn on the combi fill, allow to run through the radiator until water runs clear, do this with each radiator, add inhibitors and see how that goes.

htg engineer
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