On 01/10/2020 19:34, John Rumm wrote:
On 01/10/2020 17:50, Chris J Dixon wrote:
John Rumm wrote:

Its hard to tell from the photo how much fall it has. You don't actually
need much. You could probably get some by trimming an inch or two off
the section of grey downpipe (I am assuming the bit that goes out of the
top of the frame is just a vent and so it dropping an inch or two will
have no real effect.

Indeed. AIUI you don't need too much slope before you get the
other problem where there is insufficient water to keep the
solids on the move.

IIRC the building regs say a max fall of 90mm per m for a soil branch
connection.


The lateral to vertical connector is a 92.5 degree angle,
when measured from below (87.5 degrees above). As long as
the lateral connection in inserted straight then the
fall should be correct. That's how I always interpreted it,
though many modern houses have the lateral connection hidden
between ceiling and upstairs floor and break this rule if the
loo is too far from the stack.