Water main stop tap replacement

1 Jan 2005
Reaction score
United Kingdom
I need to replace the stop tap entering the house. The water main pipe in is black 25mm MDPE into a concoction of fittings to a 22m stop tap. I would prefer to fit a direct 25mm to 15m stop tap (poly stop tap?) with a drain cock above it into the existing 15mm copper tube. I have not had to replace any fittings on MDPE pipe before, although I have done extensive work with copper fittings. Can anyone confirm the basic points to watch out for, i.e. I think I need a 25mm MDPE insert, and lubricant as well as the poly stop tap, but there might be other factors to MDPE fittings I need to know. Any help would be much appreciated. :?:
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Are you sure your incoming pipe is black?
If it is 25 mm it will be blue, the black pipe is the old alkathene 3/8 bore approx 17 mm diameter.

Thanks for the reply, It is black, the external dimmention is 25mm, so I guess the internal bore could be 17mm. Problem is I can see fittings for 20mm pipe 25mm and 32mm but not this size. Fitted (or layed in the 1970s) :confused:
A strange one this.
If as you say your incoming main is 25 mm you will need to purchase a 25mm x 15mm stoptap and an insert for your plastic pipe.
Fit the 25mm end onto your plastic pipe (with the insert) and a small piece of 15mm copper in the other end. Fit a drain valve and then join up to your existing rising main.
You will turn off the supply at the boundary (recommended) :D
I am puzzled by the colour of your supply as the black pipe is normally 17mm :confused:
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Hi Again

Again thanks for the reply. Yes I did wonder! I noticed that 25mm wes referred to as "blue". The mesurement of the incoming pipe external is 25mm exactly, and it is also black. Can you confirm that MDPE pipe is messured on external dimensions. I will also check with the local water board, they should know what has been used in my locality. The fitting seems quite straight forward when I get the size sorted. Will of course turn of the boundry stop which is not shared. :D :confused:

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