I've to connect a 110mm soil pipe to an existing 4" clay sewer pipe. It
will be near enough at a right angle.

Depth will be about 750mm-900mm.


To make it roddable I will need an inspection chamber.
There is obviously a relationship between the diameter of inspection chamber
and depth to permit the use of rods.
I'm keen to install the smallest I can get away with as they are not cheap
things.
Advice please.


mark