As above really what’s the max length a soil stack can be run horizontally, it will be feeding a toilet and a basin . Getting confused by the tables below as table 2 says 15m and table 1 says 6m ? Can anyone help?
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Hello Piperdave22,
Unless there is a good reason it is always good practice to put a Vent pipe at the end of a long Soil float pipe.
Not doing so in some circumstances would mean that the float would not be approved by the Local Authority Building Control Officer.
After liaising with a Local Authority Building Control Department / Building Control Officer to get approval for what I had planned I have run a Soil float pipe
30 metres along a Building picking up 6 Office Toilets / W.C. & Basins and 2 Kitchen Sink wastes but I installed a 100mm Soil Vent pipe at the end of the run and behind every branch from a W.C. Pan [externally] - and of course there was a Vent on the 150mm Soil stack.
I probably could have only installed a Vent at the end of the run and 2 more equidistant along the float between the end and the Soil stack but for the sake of not much more work and materials I wanted to ensure that in the unlikely event of all of the Toilets being flushed simultaneously none of the W.C.`s / Basin or Kitchen Sink traps would be siphoned.
This was done / approved by the LABC because there was no way to install new Drainage to take 3 additional Soil stacks [which would have been the `normal` way to go] because the land below the new Toilets etc. was owned by another Company and could not be excavated for Drains because of there being a brick paved Car Parking area with Electrical cables / Water Mains and Fibre Optic cables adjacent the wall - nor would the owners have allowed Drains to be put there.
If You want to install a long Soil float either very close to the prescribed length limit or over it I would always advise venting at least the end of it.
But very importantly - as other Members have correctly advised You should always obtain Local Authority Building Control approval for what you plan to do otherwise any `non approved work` would be condemned and Labour and Materials wasted as well as your reputation with the Client damaged.
Chris