How to drain a central heating system ?

Ebe_Scrooge

Well, I know how to drain it down as such, but I've got a very odd situation in my new house. In the garage are 4 drain cocks. They are all the same, and look like standard drain cocks you'd find on any heating system. Why 4 ?

If it makes any difference, the hot water tank is a MegaFlow, and I think it's a sealed system of some sort because the label on the side says it been treated with Sentinal X100 Inhibitor, Do Not Drain.

So , I need to drain my radiators to change a valve, but how on earth can I tell which drain !!!! is for the radiators ? I don't want to inadvertently drain the hot water cylinder, and I'm guessing one of the drain cocks may be for that. I can't really physically trace the pipe runs - at least, not without ripping up every floorboard in the place.

It seems a very unusual setup to me, and I realise that it's going to be hard for anyone to offer advice without seeing it, but ....... any ideas ????

WestonDave

I'm no heating engineer so take this as you choose, but could you try tapping each drain point and seeing if you can hear a difference in the sound generated in the radiators. In theory the one on the actual radiator circuit should sound louder on the nearest radiator? You'll need someone else to listen while you tap (or vice versa) and maybe a couple of mobile phones to communicate while you do it. Its certainly not foolproof but depending on the clarity of the results you may be confident enough to proceed.

ormus

drain a bit out of each co ck.
the water color will give a big clue. CHW will be dirty/rusty. DHW should be clean/ish.

Ebe_Scrooge

Thanks for the ideas - will give them a try and see how we get on .....

Tucker

Have you tried turning on the heating alone and seeing if the pipework to any of them is warm?

Ebe_Scrooge

No, but that's another good idea to try, thanks.

Wookey

Run your heating on rads only if possible, the flow pipe should heat up to same temp as the rads and its return should be about 30 degrees colder, a draincock on either should suffice.