Cloakroom Toilet

[ajhollis]

Does anybody know what is the recommended drop for a soil waste pipe? I have to run a 2m length of pipe from my cloakroom before it meets the soil downpipe from the upstairs bathroom. There is a slight drop but not a great deal at present! Need a solution!

[teash]

The fall on the pipe should be 1 in 40, so that's 1 1/2" in 5 feet. Hope this helps

[buildersmate]

Although it might seem tempting to put in a greater slope than this, the logic is that it makes the water run faster through the pipe and it can syphon out the water from the U or P trap that you want remaining in there.

[gasman]

And how we come to that figure is the ..Maguire's Rule used to determine self cleansing gradients with intermittent or low-flow rates and is based on a calculation in which the pipe diameter is divided by 2.5: for example, 100mm divided by 2.5 = 40, therefore 1:40. the drop in depth ( fall ) over 1m would be ( 1/40=0.025m ) or 25mm.

So to answer you're question over a 2m length then 50mm of fall is you're answer.

Just Two other points to mention and help you out if you are DIY'ing this project and not using a qualified tradesman registered to self certify then.

1, You need the council to inspect and pass you're work !!! as sanitary drainage requires BRA.
2, The lowest connection to the soil stack must be a minimum of 450mm above the invert of the drain on a 3 storey or less building and min 750mm on taller buildings.