New outside tap won't drain

[dave22]

I have just replaced an old outside bib tap with a new one. The new one has a double check valve built in; I'm not sure about the old one as I haven't managed to unscrew it from the old wall-plate to look inside.

Two queries:

1) With the old tap, I was able to drain it by shutting off a designated stopcock inside the house and leaving the tap open. However, the new one doesn't seem to want to drain at all. Is the double check valve preventing water from just flowing out when it isn't under any pressure?

2) Given that I can't drain the new tap, and that the pipe burst because I forgot to drain it last winter , I guess I'm going to have to get some sort of lagging to prevent future bursts. What do you folk recommend for this? Is it necessary to put lagging around the body of the tap too?

Dave

 

[JohnD]

lagging doesn't prevent freezing, it just delays it

maybe you can put a drain inside the house for that bit of pipe?

You can get thick BS grade Climaflex and similar which is a stiff polythene foam, and they do readymade covers for taps. Be sure you make all joints very tight and tape them up, as any gaps in the insulation will be a weak point.

People use to make wooden covers for outside taps, amd insulate inside them. Looked a bit like bird-boxes.

 

[dave22]

Many thanks for your reply - much appreciated.

I can't drain the outside pipe from inside the house, as it runs along the outside wall at a slight decline to the horizontal.

I have since managed to disassemble the old tap, and can confirm it did not have a double-check valve. However, after swapping the taps over as an experiment, even the old one doesn't drain now...

I have now realised what the problem is. By cutting off the burst part of the pipe to replace the tap, the remaining pipework now has a smaller height drop from where it leaves the house to where it enters the tap. The height drop is only about an inch now, but the water has to go up an inch inside the tap before coming out, so not even a drop can drain now...

As a last resort, I can always unscrew the tap from the wall-plate before each winter to drain the pipe, and screw it back on again with more PTFE in the spring.

(I can't face taking everything apart, lengthening the pipe, drilling more holes into the wall for the new position of the wall-plate, and effectively starting again from scratch... Given my fear of all things plumbing-related, it's a miracle I've got this far without nuking the house. )

The lagging suggestions you mention look good, but if they only delay freezing as your first comment suggested, I may end up with another burst pipe if we get a particularly cold spell...?

Dave

 

[JohnD]

I would have thought you could put a drain-off-cock on the pipe at the lowest point, and open it each winter after you have shut off the indoor stop-cock to the outside pipe?

I would turn the DOC so that it points away from the house, as one day you will turn the stop cock back on without remembering to close the DOC.

 

[Boilerman2]

Why not turn off inside and simply unscrew the tap from the back plate

 

[dave22]

Yup, already mentioned that option in my second post. I have found another solution: rotating the tap so that what was vertical before is now parallel to the pipe. The water doesn't have to rise in the tap anymore - it just descends at the same gradient in the tap as it does in the pipe.

Looks a bit unusual but drains perfectly now!