CH Problem

[John]

My CH seems to have a problem. Over the last couple of days some of the downstairs rads have taken ages (2 hrs +) to get hot, upstairs (and some downstairs) hot in 10 mins. It is not a 'bleeding problem' and totatally new, I have lived here for 10 years! I think I have a blockage somewhere in the downstairs pipework. Before I pay somebody £300+ for a powerflush is there any way I can do it my self? I am very confident in removing radiators and draining down etc. but what is the procedure for 'power flushing'? I have got a Karcher pressure washer but I think sticking that in the header tank on full bore will not work!

[Andy Wade]

Firstly check the pump - it may have failed, leaving you with only gravity circulation, which will obviously strongly favour upstairs. Remove the pump's bleed screw to expose (on most designs) the end of the shaft. There is usually a screwdriver slot in this end which you can use, with the power off, to see if the shaft is free to rotate, or whether it has seized. Then with the power on and the aid of a torch, see whether rotation can be observed.

If the pump isn't running it will usually need to be replaced, but before doing so check for any electrical fault causing it not to receive power.

HTH

[Dave Plowman (News)]

I'd say that amount of 'gravity circulation' would be rare to say the least - otherwise you'd never be able to control the temperature with a thermostat.

[Andy Wade]

It's certainly something I've seen though, and is consistent with the much faster circulation upstairs, compared to down.

A 'stat controlling only the pump? Quite antiquated, that, and often associated with the upstairs rads getting hot when the heating is supposed to be off, unless a vertical check valve is fitted.

Anyway we don't know much about the system in this case, and my point was just that I'd check the pump first as it's so easy to do.

[Martin Pentreath]

Has anybody fiddled with the rad lockshield valves? It could be that the system has gone out of balance with the water taking the path of least resistance through the system and barely circulating through some of the rads.

[John]

Has anybody fiddled with the rad lockshield valves? It could be that the system has gone out of balance with the water taking the path of least resistance through the system and barely circulating through some of the rads.

Not that I am aware of.

Cheers

john

[DIY]

It depends on how bad the sludge is. You could try turning the upstairs radiators off and see if that moves the sludge in the downstairs circuit sufficient to let water circulate. If that doesn't work you could try connecting hosepipes to the drainage valves (if they have been installed) and letting cold water run through the system. That leaves removing the rads and flushing them out, or hiring a power flushing machine - Google for how to power flush central heating system. The Karcher idea is a non-starter unless you use it to flush out rads that you have removed.

[Terry D]

I would try a flushing liquid, such as Fernox or Sentinel. Drain the heating system and refill adding the flusher to the header tank. Let it circulate through the system for a few days or according to the manufacturers instructions, then drain and refill. Drain again and flush with water from the header tank to remove the flushing solution. Make sure you completely fill the system at all stages by bleeding the radiators. Finally fill the system, adding a good quality inhibitor, and bleed all the radiators, preferably with the water hot and the pump off.

Has your system always contained inhibitor? If not, you could have corrosion problems. The next plan would be to remove the offending radiators, take them into the garden and use a hosepipe to back-flush - much like a car cooling system. Remove the bleed screw and also the large screw in plug from the top LHS of the radiator. You will need a suitable tool to remove this - its like a large Allen key with a square fitting (obtainable from sheds). You may need to use PTFE tape when replacing. If you're confident with radiator removal, I certainly wouldn't waste £300 for a power flush.

Terry D.

[Martin]

< snip >

That's interesting. I've also bled with the pump on, so evidently been doing it wrong :-( What is the reason, please?

[Terry D]

According to my research, bleeding with the pump running can suck air into the system. However, I find this difficult to believe - I have used both methods in the past with complete success.

Terry D.

[Broooz]

I used to bleed with the pump running but then I started getting air in the system and the gas man said that was the cause. I now always bleed without the pump running and that cured it.

[John]

I did all this in Dec 2004 I assume the inhibitor will still have some life left in it.

The house was built in 1992, we bought it in 1997 in the loft was an empty bottle of inhibitor dated some time in 1997 so presumably the old owner did it then.

I do this every time I decorate a room while the rad(s) are off for decorating purposes.

I was thinking the same but was worried I could be wasting my time if the blockage is in a pipe rather than a rad.

Cheers

John

[John]

Thanks for the advice I will try turning the upstairs off and see if that helps, problem is I now have to wait untill everything cools down. The Karcher idea was actually a joke but I forgot the smiley ;-)

Cheers

John