Leaking stopcock on old Alkathene pipe. Yikes!

[The Bedwetter]

I have a problem with an old stopcock (40 years?) fitted on the old alkathene supply pipe. This is in a property owned by an elderly friend and the stopcock has been leaking from the spindle for many months. Despite several attempts to pack out the gland with PTFE the valve continues to leak. My preferred option would be to replace the stopcock altogether but was discouraged from this by a couple of local plumbers in the nearby merchants who believe alkathene – I have not come across this stuff previously as it seems not to be used in London - is a difficult material to work with and I would be better to try to get the stopcock apart and replace as many parts as possible from the merchants.

Despite my best efforts using a set of footprints and an adjustable spanner I cannot get any movement on the upper part of the valve as there is limited room for movement under the kitchen sink. So for the moment I have left the valve with a few squirts of WD40 (OK, a bit desparate) around the fibre washer with a view to returning tomorrow.

If further efforts to dismantle the stopcock prove futile then I will require to replace the thing, whatever, despite the other plumbers’ misgivings. I am unable to give a true specification of the alkathene suffice to say that its diameter is 28mm. I originally purchased a 28mm stopcock for copper pipe with reducing set for the 22mm copper side though the guy behind the counter in the merchants is uncertain as to whether this should be used here. So I think it might be best to buy one of those Plasson or Philmac valves that come with varying sized adaptors (universal couplings?) and hope this can be made to fit. I can find no sign of any coloured printing on the pipe itself but from the table below the nearest I guess it may be ¾” class C.

I would have thought that this type of pipe would come with inserts but the one of the guys in the pm’s does not think this is the case. Surprised to hear this, though.

Suggestions from anyone who has experienced the joys of alkathene would be much appreciated.

Approximate Alkathene Pipe Sizes​
Pipe​	Class C ID​	Class C OD​	Class D ID​	Class D OD​
3/8 inch	12mm	17.5mm		17.5mm
1/2 inch	15.5mm	21.5mm	14.1mm	21.5mm
3/4 inch	19.5mm	26.9mm	17.5mm	26.9mm
1 inch	24.5mm	33.7mm	21.9mm	33.7mm

ID markings on the pipe blue writing for class D or green writing for class C.

 

[townfanjon]

The last one I came across took longer to source the parts than do the job , the liner and fitting are very hard to get hold off , firms say the have them , but when you order they say they haven't got them , I may have been unlucky.
Just fit a philimac.

 

[steadyon]

1. Wrapping PTFE tape around the gland nut is not how its done.
2. To reseal a gland nut:
2a. Fully open valve in the usual way.
2b. If there is a screw holding the handle to the spindle, remove screw and remove handle.
2c. Clean all accessible parts of spindle to remove limescale corrosion etc. Polish with fine wire wool, Scotchbrite, very fine emery as much as possible.
2d. Temporarily refit handle if removed and turn off the water via the handle.
2e. Undo the gland nut. This is the smaller nut nearest to the handle. Slide gland nut up spindle, and no harm in removing it altogether if possible if handle comes off.
2f. Take a 300 mm length of PTFE tape (ordinary, not gas PTFE. If using gas, use less) and twist it into a string. Wrap string clockwise around spindle, and using gland nut push it down into the "works" of the tap.
2g. Replace gland nut and tighten until spindle turns, but is stiff.
2h. Turn water back on and check for leaks.
2i. Repeats as necessary using more PTFE until satisfactory.

 

[EvilDrPorkChop]

1. Wrapping PTFE tape around the gland nut is not how its done.
2. To reseal a gland nut:
2a. Fully open valve in the usual way.
2b. If there is a screw holding the handle to the spindle, remove screw and remove handle.
2c. Clean all accessible parts of spindle to remove limescale corrosion etc. Polish with fine wire wool, Scotchbrite, very fine emery as much as possible.
2d. Temporarily refit handle if removed and turn off the water via the handle.
2e. Undo the gland nut. This is the smaller nut nearest to the handle. Slide gland nut up spindle, and no harm in removing it altogether if possible if handle comes off.
2f. Take a 300 mm length of PTFE tape (ordinary, not gas PTFE. If using gas, use less) and twist it into a string. Wrap string clockwise around spindle, and using gland nut push it down into the "works" of the tap.
2g. Replace gland nut and tighten until spindle turns, but is stiff.
2h. Turn water back on and check for leaks.
2i. Repeats as necessary using more PTFE until satisfactory.

As Steadyon says, but I like to use Loctite 55....

 

[SimonG]

Isolate outside. Cut a bit off the alkathene. Trip to merchants for necessary bits. Return. Sorted.

 

[Scott_D]

Looks like you have plenty of space for a universal fitting and a new valve

 

[The Bedwetter]

Thanks very much for the comments, guys. I took steadyon's advice and thoroughly cleaned up the valve and applied new PTFE. This has entirely stopped the leak and have simply added a 22mm stopcock to the pipe downstream for any isolation etc.