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Hi all

I need to drain downmy combi central heating system to put a new rad and valves in each end. The drain cock downstairs isn't opening properly and it started to leak once fully turned off. It might be a type B drain cock (picture attached) which has been put on my 15mm compression.

Any ideas how to drain down without flooding the place as need to remove the drain plug!

Thanks very much

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Hi there.

This is only DIY'er advice from my experience, follow it at your risk. But I had this problem, and the valve was leaking around the part that you unscrew instead of coming out of the pipe, but in my case, this stopped happening when the valve was fully open.

In other words, open it half a turn and it drips out of the valve part, but open it half a dozen turns and it stops dripping and flows from the pipe.

Probably best to wait for someone who knows to confirm if this is possible before you try anything. It happened to me but I could be an anomaly.
 
Hi there.

This is only DIY'er advice from my experience, follow it at your risk. But I had this problem, and the valve was leaking around the part that you unscrew instead of coming out of the pipe, but in my case, this stopped happening when the valve was fully open.

In other words, open it half a turn and it drips out of the valve part, but open it half a dozen turns and it stops dripping and flows from the pipe.

Probably best to wait for someone who knows to confirm if this is possible before you try anything. It happened to me but I could be an anomaly.

Thanks very much mate. I think the jumper may be stuck etc but it could work what you're saying to do.
 
I would close off a radiator both sides at the lowest part of the property, drain that rad down and remove, a wet vac would make it easier but it can be done the old fashioned way with a shallow tray and a bucket to empty that into.

Then I would put a short piece of copper into a 1/2" garden hose using a jubilee clip and connect that to one of the now available rad valves using a nut and olive and drain it down through that valve. Once your system is empty you can replace that faulty drain off (I'd install a full bore ball valve for more long term reliability) and do the work you need to do.

If there is still some water in the system after that it shouldn't be a whole lot so you might then get away with undoing the compression fitting on the old drainoff and get the last of the water out there into a tray then a bucket again.
 
I would close off a radiator both sides at the lowest part of the property, drain that rad down and remove, a wet vac would make it easier but it can be done the old fashioned way with a shallow tray and a bucket to empty that into.

Then I would put a short piece of copper into a 1/2" garden hose using a jubilee clip and connect that to one of the now available rad valves using a nut and olive and drain it down through that valve. Once your system is empty you can replace that faulty drain off (I'd install a full bore ball valve for more long term reliability) and do the work you need to do.

If there is still some water in the system after that it shouldn't be a whole lot so you might then get away with undoing the compression fitting on the old drainoff and get the last of the water out there into a tray then a bucket again.

Thanks very much and a brilliant way to tackle it. The only problem I have is that there isn't a TRV head on this rad (flow side) but the return side is available. Picture attached. I'm guessing you can't just drain down via the return?

Thanks again fella

20170926_165616.jpg
 
Unfortunately not. You'll either need a decorator's cap to shut that valve off or take out a different radiator that can be closed both sides.
 
As long as it is a sealed system you could try this if you're confident. Don't blame me if it goes wrong!

If you turn the isolation valves off under the boiler and release the pressure in the system into a bucket from the air vent and make sure any auto air vents are closed you will then (normally) have the finger over the straw effect. You should then be able to open the tap fully and push a thin screwdriver up the spout to prise the washer off the seating. Have the hose ready to push onto the spout.
Failing that, you will in theory be able to take the drain tap off at the compression nut and service it or replace it and use that to drain the system.

If you are not confident and competent with plumbing, you would be better off getting a Plumber or Heating Engineer in to sort it for you. These methods can lead to other issues. One example I can think of is the isolation valves under the Boiler may begin to leak if they are of poor quality or have never been turned off.

Like I say at the start, I am not responsible for any disaster or failure. Just offering information in case you are a competent DIY'er
 
Take pressure off, get another doc with compression nut n olive ready to tighten, swap over with a rubble bag underneath. There will be a little water but if your quick it will be fine.
 
If you're confident repairing the pipe afterwards you can use a self cutting drain valve at the point most convenient i.e. Closest to the back door or whatever.
 
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