Plastic Pip Fittings

[jos22]

I have a caravan & the external water pipes are all plastic. They change to copper where they enter the van. On tne external pipework I need to change two bends to drain off points. ie change the bends to tees & insert some sort of drain off mechanism. The present plastic fittiings are a bit like the brass compression fittings. You fix by putting the screw cap on the pipe, followed by an O ring, a firm plastic washer and a metal "washer" that grips the pipe. Youn then screw on the remainder of the bend.

What I would like to know is:-
How do I get the "metal" washer off the existing pipe?
What type of plastic tees do I need? Are they just called plastic tees?
What is the correct name for the drain off mechanism? (Like the drain off valve on heating systems)
Can I connect the drain off direct into the tee? (As if it was just a pipe).

The water in the pipes is fed from the mains, although the pressure is quite weak. I tried to attach a picture of what I meant, but even that defeated me, so you can see I need help.

Many thanks



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[chrishutt]

You can drain the pipework by undoing the existing push-fit elbows. No need for any drain-off valves!

 

[jos22]

Thanks but I do know that.
Over the winter one of the bends that I want to replace has obviously still had some water in & frozen, breaking the screw on end. As I need to replace this I thought I might as well go the full "hog" and insure that next year I can drain that part completely (& easily). Hence I would like to put in another drain off valve.

 

[chrishutt]

If you need to remove a damaged "nut" then you'll have to remove the grab ring - easiest thing is to cut the pipe just up from the ring. Replace the elbow with a tee and fit whatever drain valve you like to the third branch of the tee. If you want it to be easy to use don't bother with drain-off valves - use an isolating valve or stop tap.