Hi, have built new upstairs bathroom between the two bedrooms in my
2-up 2-down and now need to install the soil pipes.

I have a length of 6m brown pipe - is this ok for running under the
floorboards for the horizontal run to the rear of the house, or must I
use grey socket pipe (the toilet flexi connector pipe will go into the
end of this pipe so I think I don't need the socket anyway)?

This pipe will connect outside to a black 92.5 access branch, going up
to the terminal vent and down to a rest bend, using black single socket
end pipe. I got an access pipe just in case of a blockage in the
future. However the access pipe has 3 sockets. Do I remove the socket
from the end of the vetical pipe to connect to the access pipe. If so,
the joint will now be upside down - hopefully I am worrying about
nothing.

Thank you