Cleaning the CH system after fitting a new towel radiator

7 Dec 2006
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United Kingdom
I am replacing a radiator in the bathroom in the next few weeks with a towel radiator and the manufacturers instructions state that a full system clean is mandatory in order not to void the guarantee.

I understand this will be to flush any flux or other debris introduced to the system.

I have a central heating cleaner solution which I am going to use for the job and the instructions advise this be left to circulate for anywhere up to 3 weeks.

I would like to let this circulate for a week or two in order to let the cleaner get to work (the system is a combi system in a ground floor flat with 5 radiators in total, around 18 years old). The central heating has always worked fine and I don't believe I have any sludge problems to worry about.

My question is, is it ok for me to leave the cleaner circulating for a week or two and then drain (and refill and drain several times)?

I am a little concerned that perhaps I need to flush it after only a day or so to avoid any damage that may be caused by debris introduced when fitting the new radiator.
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If you are fitting a brass towel RAIL then you dont need to bother with any water treatment.

If its steel then you can leave a good quality cleanser in for the recommended time. My Sentinel X300 cleanser says 2-3 hours !

After cleaning you must change the water a couple of times and add a suitable inhibitor. I use Sentinel X100.

Is the debris assumed to come from the new radiator/towel rail ? If that's the case, can't it be cleaned/flushed before adding to the existing central heating circuit, avoiding having to flush the whole lot ?

e.g. if I want to replace a radiator with a new one of the same size, could I do the following:-

0. buy radiator/towel rail.
1. flush with a hose, add some water+X300 and bung up the radiator for a couple of weeks, then flush again.
2. close valves on existing radiator, remove old one after draining into a bowl.
3. move brackets on wall, attach connectors to radiator
4. hang radiator on wall, join existing valve to radiator
5. add a bit of inhibitor to the radiator
6. open valves to radiator
7. top up system pressure

I would expect the manufacturers are wanting to protect themselves from problems from the pipework and the EXISTING system.

Leaving X300 in a static rad will not do much good as it has to be circulating and warmed up.

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Thanks Gents, yes I believe the manufacturers want it warmed up.

I will no doubt hose out the radiator first anyway.

In essence I just wanted to check that any flux or debris that could have crept in, will not corrode the system in the 1-2 weeks that the cleaner is circulating the system.

After that duration I will drain the system and then intend to refill it and drain, 2 - 3 times, then fill and add an inhibitor product. (Fernox Concentrate)

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