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Just answering by memory here and on the fly : Anything "not underground" is considered a drain, where as anything inside the ground is considered a sewer, So the rule min 65 only applies to a sewer. When you do an underslab and have a foorwaste, you can charge that floorwaste with a 50mm pipe (also considered drain) after the floorwaste it has to be 65mm (considered sewer). Then you can calculate the drainpipe size by using your fixture units. Hope this helps! ;D
The only mistake I see is the 60mm LOL
hey karma , thanks for your response. In the modal answer that they give they have a 40mm discharge pipe connecting into the main suspended drain so I dont think theyre using drainage princibles. Just not sure what rule they are applying to this system. I have contacted Jose at the board and he reckons he will forward it on the the appropriate person. See how we go!!!!
Cheers
I think the drawing is wrong also. They also state gradients of 1:60. This is too flat for 40mm and 50mm.
How have you gotten on with this?