Replacing Old Stop Tap on Old Imperial Pipe

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PolarNorth78

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Morning All,

My Stop Tap has seized up and the good old spanner and lubracating spray hasnt helped. Ive attached an image as its a bit of a dogs dinner and will need a lot of tidying up (plumbing under the sink is a right mess).

The layout:

1) What appears to be 1 inch black imperial pipe into the stop tap

2) Out some 3/4 inch pipe (think its plastic)

3) Compression reducer to 15mm copper

4) 1/2 bore valve (presumably installed when the kitchen was done instead of replacing the stop tap)


Tap flow rate is approx 17 litres per minute.

I would like to replace the stop tap with a new one and into a 22mm copper pipe. This will then replace all of the 3/4 (up to first floor) and 1/2 inch (first floow to water tank in the loft) black alkathene pipe in the house (it was built in the 1970s and there was a copper shortage at the time). I am torn on whether to install a full bore isolator valve afterwards as a back up.

With all of this in mind:

1) How is it best to connect to the old pipe? I have used the multi diameter plasson connectors (https://www.cityplumbing.co.uk/p/pl...t-22mm-x-24mm-to-28mm-pp10017c022028/p/775644) before but they take up a bit of space which is at a premium under the sink.

2) Is it possible to deconstruct and rebuild the stop tap (or is replacement the best option)?

3) Any hints and tips - in particular from someone who has seen this set up before and dealt with the imperial pipes? I know there is a c/d internal diameter to consider. The pipes upstairs were the larger diameter and sanding down a 22mm insert did the job nicely.

4) Linked with 3, anywhere that does connections for the imperial pipes or workarounds for using metric kit on them? I know the pipes will be replaced but it helps should I have an incident before I get around to replumbing the house.

I can shut off the water externally. Hot water is gravity fed in copper and bathtub is gravity fed in copper.

Thanks in advance.
 

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Yes it looks like 3/4" alkathene coming up to the stopcock. You should be ok with a 22mm compression stopcock but swap the olive for a 3/4" one. Conversion olives will be available from any plumbers merchant. Its unlikely that the old compression nut will fit the new stopcock and removing the old olive is likely to damage the pipe. Luckily you appear to have plenty of alkathene so you can cut it back a bit. If there is an insert in the end of the pipe and you can get it out, then re-use it. If you can't get it out and you can't find a replacement, I think 15mm copper is a fairly close fit. A 1" piece tapped into the end of the pipe should do the job.
You will also be able to get a plastic stopcock to do the job but they can be a bit pricey. Philmac or Plasson should be available from plumbers merchants.
 
As above re replacement that look like 1/2 alkathene which externally was same size as 3/4 copper.
That looks like a conex stop tap many current compression stop taps use same thread pitch nuts so you may be lucky.
If not try really hard to save insert .
Alkathene was available in both class D and C
15mm tube works as a insert for class C but class D require a smaller insert as wall thickness greater.
 
Thanks all,

Super helpful! I have a confession, I've done the classic thing of a one inch pipe, is NOT one inch... So having measured it with a tape measure (I don't have a set of verniers at the moment), it's around 26mm which puts it inline with 3/4 Inch Alkathene.

Black Alkathene Pipe Size Information

We don't stock the old imperial sized black Alkathene plastic water mains pipe or fittings any more, though we do have some size information
www.stevensonplumbing.co.uk www.stevensonplumbing.co.uk

The stuff for the rest of the house is half inch and I've attached an image of the markings and connectors if anyone knows what they are and can provide some context. It also means the stuff up to the loft from the first floor is 3/8.

I've also had a look at the stop tap, it appears it uses a male compression fit threaded into the tap which may help in some format. Though I suspect it will be difficult to get off without removing the whole unit. I have about 8.5 inches of pipe underneath.

Re fitting the new stop tap, are 3/4 Inch compression fittings still a thing or is it a larger compression fitting (e.g 28mm) with say a 3/4 olive the right way (this is getting confusing, first time working with imperial pipe...)? Plan B is a plasson fitting but it uses space I'd rather save.

I've posted some images of the other pipe for users benefit, it took me a while to figure out what I was dealing with having only used metric copper.
 

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3/4” olives are available as in post #3. The grey pipe is polyorc - horrible stuff - if you can rip it out and replace, otherwise you’ll need special compression fittings for them as I don’t think the solvent weld fittings are available anymore.
 
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I should have been a bit clearer, I get the 3/4 olive, it's the suggestion of a 22mm compression for a pipe that's 26.9mm OD. I will do some googling in the meantime.

Replacing the pipe isn't an option as that involves digging up the driveway and a heap of pain.
 
PolarNorth78 said:
I should have been a bit clearer, I get the 3/4 olive, it's the suggestion of a 22mm compression for a pipe that's 26.9mm OD. I will do some googling in the meantime.
Click to expand...
Maybe it’s 28mm? Have you managed to look at the fitting nut as it’s usually stamped on
 
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