C/H System Cleaner

[John]

Bought some "Kilrock Advanced Concentrate Central Heating Cleanser" from B&Q today to try and improve a couple of sluggish radiators.

Has anyone any observations about this particular brand?

[Andy Hall]

Not really, but if the radiators are noticably sluggish (i.e. filled with silt and sludge), then these products won't make a lot of difference. They are designed to pick up the last bits of crud in an otherwise clean system and to neutralise any fluxes etc. They won't work miracles.

If the system is that bad then either it should be power flushed - you can rent the machine or machine plus bod to do this - or you can drain the system and take the radiators outside for a good pressure wash or with a mains hose.

After you have done that and flushed the pipes is the time to use chemical cleaner, normally hot and for a week, but check instructions.

Finally rinse thoroughly and use a good quality inhibitor. There is a difference between efficacy of brands and I would use either Fernox or Sentinel, certainly not DIY store products. They may cost a little bit more but you are proetecting an investment of several thousand pounds..

[John]

Thanks Andy - the radiators are removed when I decorate - they are thoroughly cleaned. My problem is either with the pipes or the manifold (8mm system). I have observed a good flow out of the return pipe - but sluggish from the flow pipe (or the other way round) when I did an investigation on one of the 2 poor radiators. I have Maxitwin valves - the flow tubes are in good condition.

The system has always had an inhibitor (20 years) and it has been flushed and changed at intervals.

I find myself worrying that maybe some settlement may have caused a pipe to get a bit squashed. However, I am hoping the clean - and a bit of additional encouragement through the poor radiators by turning off the other might fix the problem if it is only crud.

[Andy Hall]

You might be lucky.

I guess that the system is roof tank fed?

Could you try the idea of hooking up mains water so that the pipes can be pressurised? I did that with mine while converting to sealed operation and found that it blew out quite a bit of crud - all original builders and plumbers material. I don't think a chemical would have removed it.

Otherwise, I fear that you might have a crushed pipe somewhere.

[John]

I'd agree with that. We had our boiler replaced and part of the deal was a power flush of the existing system. It shifted all sorts of muck in a most satisfying way. The operator set up his pump set and turned off all but one radiator. Then he flushed each rad in turn to maximise the flow rate. As I said, a really satisfying sludge came out.

John

[John]

I made up a connection for my hose pipe - via a service valve and a screwed fitting for the top bung of the radiators. Backflushed for a while (keeping watch on header tank / overflow). Didn't help much but at least proved it wasn't an airlock. Unfortunately my house has the pipes behind the plasterboard and under chipboard floors - otherwise I would be doing a bit of re-plumbing.

I suspect that 8mm pipes can easily sag a bit and this will cause areas for sediment to gather.