Central Heating Drainage Problem - no water coming out of drain tap!!

[junklunacy]

Hi all, I've been using the forum for a while now and its been a great help with plumbing jobs around the house. However i have a problem that i cant seem to resolve myself, help.

I have gone through a series of steps to drain a wet central heating system, due a leak from a valce that I want to pack/replace.

The Gas/water off, CH system off, ALL radiators have manual valve open fully and lockshield valve open fully. Yet when i open the drain tap, no water. I've put a metal clip up the tap to see if there is any blockage, to no avail. There must be something I'm missing???

Thanks in advance

JL

 

[AllyBongo]

possibly frozen, try a blow torch on the pipe or kettle of water

 

[Henry]

I've had fun several times in the past with drain valves of the typical 'hose connection' type where after years the washer sticks in the seat (especially if screwed down unnecessarily hard I suspect) then when you unscrew it it actually pulls the pin back through the hole in the middle of the washer. Often a bit leaks out if the pin has pulled completely clear, but if it is in a sludgy point in your system the little hole could be blocked with crap.

Are you sure the metal clip went right in through the valve when you tried that?

If you have the kind of valve I am visualising, can you unscrew the internal valve gubbins right out of the barrel? (They often have a milled edge you can grip with pliers etc. the bit where the square ended shaft goes through. If you can do this, does the washer come out with it on the end of the shaft OK?
If not then it may be part of yr. problem... BEWARE!/BE PREPARED if it all suddenly comes loose you will have a horrible mess squirting out every where ! / Henry

 

[FD Powerflow]

Hate to say the obvious but have you opened a rad vent somewhere on the system?

 

[junklunacy]

Hate to say the obvious but have you opened a rad vent somewhere on the system?

thanks for your comments guys, PF, ALL valves are open as per my org post? wire pushed up the valve as poss, Henry, i am ready for the p~*** when i unlease the turn of the rad!!

 

[oldplumber]

cause of problem is previous installer soldering on drain valve and leaving nice rubber washer in valve when heating the valve up with their blow torch. So dont treat it as frozen and apply more heat as suggesteded. Strip down valve by unscrewing knurled part on valve and taking apart, reach in with small screw driver to dislodge washer. NB ensure hose on drain off, loads of towels available and keep thumb ready to put over hole when washer comes out. catch washer put on internals and reassemble to stop flood

just seen bulk of this already mentioned!!

 

[bajers]

Just read this thread and don't know if you are sorted now, but had exactly the same problem last week. Undid the drain and nothing came out, unscrewed the fitting fully and took it out and there was no washer on the end (push fit over a central pin on the fitting). Got some needle nosed pliers into the valve and pulled the old washer out and hey presto, full flood!

Remember to have a new washer on hand though (B&Q) as the old one will be knacked and you will have a constant drip if you refit it.

 

[WHPES]

Any rubber washer which has been in a drain cock for several years must be replaced after draining the system if you are to stand a good chance of getting it to reseal.

 

[stevetheplumber]

alternatives to yhe flood the floor methods
shut one rad of best is smallest drain into a container remove rad and con hose to one valve and drain

buy a self cutting drain of or use a selfcut washing machine valve to drain