Cannot drain central heating system!

[oska]

Hi, I added some cleaner to the system and now need to drain it but when I undo the valve at the bottom of the system near the boiler nothing comes out. I have gone around all radiators and bled to see if there was any air but nothing.

The system works and the rads all get hot so water must circulate through the system. It's a conventional boiler with a header in the loft. I remember draining it around 6 years ago fine when we replaced a rad.

Thanks for any advice.

 

[JohnD]

please describe the valve you mean or, better, attach a photo.

here are some examples of drain cocks
http://www.screwfix.com/search.do?fh_search=drain+cock&fh_view_size=20

When you bleed the highest radiator in the house, does water squirt out forcefully and without the pressure dropping?

 

[oska]

It's this type. The water seems to come out normally when I bleed. Just kind of trickles out.

 

[denso13]

Probably a stuck washer of full of gunk. Unscrew the nut on the bottom (not fully out) and push a bit or wire up the bit where the water would normally come out and see if it helps.

 

[JohnD]

put a bucket underneath it first!

If you did not drain a bucket out when adding the chemical to the F&E tank, it is probably still there and has not been drawn down into the system.

 

[oska]

Thanks for the replies, I think I know what it is. The bit you unscrew to drain it, I have taken the whole thing out. Looking inside there is another bit that I guess is supposed to unscrew with it. It only has a small bit on the end and I cannot get enough grip on it to unscrew it.

I'm stuck now.

 

[denso13]

Is it not just a loose plunger which is still in the fitting? This will have a washer on the end which is probably stuck to the fitting. Be careful working with the stuck bit as it could come away quickly.....as John says, keep bucket handy!

 

[oska]

Yes, that's what it sounds like. I've tried pulling and twisting it with pliers but it's stuck solid.


What a waste of a day off work.

 

[JohnD]

you can slacken off one or more of the nuts. Water will dribble out. the way the cock is attached, to remove and replace it you would need to be able to pull the two pipes apart by an inch or so.

you can also try poking it through the drain spigot with a small screwdriver or bit of bent wire hanger.

When it goes, you will need two thumbs to block the gush, and an assistant with two large buckets. You may be able to push a hosepipe on the spigot while it gushes, and screw the end back on against the flow. The system probably contains about 20 gallons.

 

[ljrgas]

if your having to much trroube buy one of these

Untitled

• ljrgas
• 13 Sep 2013
• 1

however after you have drained it down I recomened removing it and replacing existing

 

[bellairaphon]

If you can isolate a small rad at both valves either side. Then remove the rad and drain from the valves. Whilst its empty replace the Drain valve.

Nath

 

[JohnD]

yes, and you will often find that a garden hose screw-connector, or a washing-machine-hose end, will fit on the radiator valve.