Gradient on the discharge piping from a Saniflo

[oph]

Soil pipe is designed to operate with solids which need a lesser fall!

Brunel Uni used to have a demonstration with clear plastic tube showing that at a steeper angle the solids are not moved! Its rather counter intuitive.

You are right that they will operate down to 22 mm which would normally be in plastic but thats a minimum size and the larger is best when any significant distance is involved.

Tony

Tony, 22 tube is best for several reasons.

overflow sags easier and more importantly come apart easier under pumped pressure as the pipe gets older. If its done in copper tube join it under the floor in compression fittings AND use PULLED bends rather than 90 elbows. Reason? easier to disassemble in the future when it blocks when the unit breaks down and trust it will. It isnt pleasant and as an apprentice i used to have to take those things apart and change the internals on them.......... I had a taskmaster for a boss but i thank the bastard for it.

And you dont want to chew too much out of potential 7 inch joists in victorian houses trying to accommodate a 35mm pipe