Attaching mains stopcock to a ~22mm (OD) plastic pipe

[mikej2005]

I need to replace my mains water stopcock. It's attached to what appears to be a 22mm (or closest imperial equivalent) OD black plastic pipe that enters the house through the floor. The house was built in 1972.

Pic : http://i55.photobucket.com/albums/g136/mikej2005/stopcock_02.jpg

I've searched around on this forum and found quite a potentially useful thread here : www.diynot.com/forums/viewtopic.php?p=479298#479298

From the thread, it looks likely to be "black alkathene pipe" or "½" black low density polythene pipe (BS 1972) which has an OD of 21.5mm. (same as ¾" imperial copper)".

As you can see from the pic, I can't really afford to lose too much on the length or it's in danger of being below floor level, so taking a sample to a plumber's merchants might be tricky !

Does anyone have any suggestions or tips on how to attach a new brass stopcock to a plastic pipe like this ?

The thread mentions that a 'Plasson' or 'Philmac universal coupler' fitting could be used to convert to 15mm copper (for example) - could a coupler like this - www.philmac.co.uk/Products/UTC.asp - be used, followed by a conventional 15mm stopcock ? Would it be acceptable to have a fitting like this before a stopcock ? (Water can also be turned off at meter in the road outside)

Incidently - the current stopcock doesn't shut off the supply properly when turned off, leaks when fully opened and the run-off part also leaks when used too, so I'd rather replace it than simply add another stopcock above it.

Thanks in advance for any advice.

 

[chrishutt]

You just need a 22mm stop valve with compression ends. Replace the 22mm olive in the upstream end with a ¾" olive and attach to black poly, but keeping the copper liner inside the end of the poly. The outlet of the stop tap can be adapted to 15mm by a reducing bush or other standard reducing fitting.

Alternatively you might try just replacing the headgear of the old stop tap with the headgear from the new 22mm stop tap. If they're both made to good old BS 1010 then the headgear/body thread should be the same. then you won't need to interfere with any of the pipe connections.

 

[mikej2005]

Thanks for the advice.

I think a 3/4" olive will be too small for the plastic pipe though - are they exactly 3/4 " ?

I've measured the pipe with calipers and it's very close to 22mm, so not as small as 3/4" which is more like 19mm ?

 

[chrishutt]

¾" is a nominal size (refers to bore of pipe), it's actually the size suitable for pipe with an OD of 21.5mm, but you would ask for a ¾" olive in a plumbers' merchant. It would normally be used to adapt a 22mm compression end to old imperial ¾" (nominal bore) copper tube.

As I said, it might be simplest just to change the headgear of the tap. Providing the seating in the tap body is OK that should sort it.

 

[bobthebender]

Chris is right.