"ducting" for replacement water main

[texteditor]

Will be replacing water main soon what should I use for ducting through the wall?
Does it have to be rigid or could I use the flexible concertina type?
Thanks, texteditor.

 

[MANDATE]

Your 'water authority' would be the best place to answer your question.
The purpose of the ducting is to hold adequate insulation and when I replaced a water pipe I had to use 100mm (4in) ducting and the insulation was about 3in outside diameter.
I used the straight 'rigid' type with a 45 degree bend at the bottom.
I can see the advantage of the flexible type and dont know on what grounds it could not be permitted, providing you can get the insulation in it.
Also I used 2in ducting in the bottom of the trench (without insulation) which was easier than replacing cinders with sand and makes replacing the pipe easy if needed.

 

[Blagard]

This is a typical guide

http://www.unitedutilities.com/documents/1344_How_20to_20lay_20new_20pipe.pdf