Drainage below kitchen floor Drainage and wastage systems and plumbing help, advice and answers

[rodz]

Hi i want to fit a kitchen sink with a garbage disposal unit. the problem i have is its on the opposite wall to the outside drain. and running it around the out side isnot possible. i m digging my floor up anyway so i want to put it in there but how would this be done? what size pipe do i use? how deep does it have to be. any other way i could do it? thanx

[dodgepott]

Yeah i would put a 2 inch waste pipe in with as much fall as possible with a rodding point at both ends.the cover over the pipes depends on the fall of the waste pipe.I would guess 50mm cover min where there is a lot of traffic.

[Nester]

Agree that 2" pipe would be the minimum size for near horizontal runs for free flowing waste water. The less the fall, the more the build up of soap and fat deposit in the pipe.
However, if the waste water was pumped you could reduce to 32mm. The way to do this is to use a Saniflo macerator under the sink which not only macerates but pumps away the waste, working only when a certain level of waste and water is reached. Saniflo are best known for their toilet macerators - these can happily push human waste for a short distance down a 20mm pipe!
The snag with pumped products like this is that you are dependent on electrical power. No power, no waste disposal. Saniflo products are flow switched -they work automatically - but remember that all macerators and pumps make noise.