Draining CH system

We've got an open vented central heating system with a F&E tank in the loft and feed and return pipes to all the radiators. There's currently a couple of bottles of sludge remover in the system, which has been doing the rounds for about a month, and now needs to come out and have an inhibitor added instead. The questions I've got about this are:

1. Would you drain off from just one downstairs radiator, or is it better to do it from more than one at the same time?

2. Would it be better to stop the water coming in through the expansion tank, empty the system out altogether and then flush more water through, or would you just let the water keep going through until the water coming out is clear?

3. When it comes to adding the inhibitor, will it work its' way through the system just by putting it in the expansion tank, or is it better to put this in while the system is only half full of water?

Thanks in advance for any help - as always, much appreciated.

c00 said:

1. Would you drain off from just one downstairs radiator, or is it better to do it from more than one at the same time?

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Depends on the route of the pipework - if it drops vertically to feed a subset of downstairs rads, then that water/sludge won't drain out of those ones unless you drain from that loop of pipework.

2. Would it be better to stop the water coming in through the expansion tank, empty the system out altogether and then flush more water through, or would you just let the water keep going through until the water coming out is clear?

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Best to flush until clear.

3. When it comes to adding the inhibitor, will it work its' way through the system just by putting it in the expansion tank, or is it better to put this in while the system is only half full of water?

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I would add it immediately after turning on the water and before venting any rads.

Remember to vent all upstairs rads before running the pump.

If the system has been really dirty, consider buying a Magnaclean and leave in place for some time after adding the inhibitor. You might be surprised...

Softus said:

2. Would it be better to stop the water coming in through the expansion tank, empty the system out altogether and then flush more water through, or would you just let the water keep going through until the water coming out is clear?

Click to expand...

Best to flush until clear.

3. When it comes to adding the inhibitor, will it work its' way through the system just by putting it in the expansion tank, or is it better to put this in while the system is only half full of water?

Click to expand...

I would add it immediately after turning on the water and before venting any rads.

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Hi,

Sorry - just to clarify - are you saying to keep the water coming through into the F&E tank while you're draining off the rads? (The reply to the last question suggests I need to turn the water off).

Thanks in advance!

c00 said:

Sorry - just to clarify - are you saying to keep the water coming through into the F&E tank while you're draining off the rads?

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You can flush in any way that suits you. For example, you could do as per your postulated method of leaving water running into the F&E. Alternatively you could shut the drain off after draining and let the system fill up again, then drain again, then fill again, then drain again, etc. etc.

(The reply to the last question suggests I need to turn the water off).

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Your interpretation is a bit odd. It's just a matter of logistics - even if you shut the drain while the F&E is filling then most rads would remain full of air, such that you could add the inhibitor to a 'full' F&E (as long as it doesn't overflow of course) and then vent the rads to draw the solution into the system.