Want to install a new drain line for a toilet, but it would have a slope of 7/8" per foot. Code only requires that slope be at least 1/4" per foot. Want to know if using this much steeper pitch would create flow problems. Thanks.

Hi JP

A 1/4" to a 1/2" per foot of pipe is ideal. I wouldn't want to run a 100 foot run of pipe at 7/8", but if we are talking say 5 or 10 feet maximum then you should be just fine here!

Mark

Too much slope and the water runs so fast it leaves solids behind. Too little and the solids drop off and the water runs out. When I was out there we ran 2" at 1/8" to the foot and 3 and 4" at 1/4" to the foot although I remember running 10 and 12" cast iron mains at 1/2" to the foot. Regards, Tom

Thanks a lot! The new PVC drain line would only run 5 to 6 feet to the old cast-iron drain, so I'll go ahead with the 7/8" pitch.

Too much slope and the water runs so fast it leaves solids behind. Too little and the solids drop off and the water runs out. When I was out there we ran 2" at 1/8" to the foot and 3 and 4" at 1/4" to the foot although I remember running 10 and 12" cast iron mains at 1/2" to the foot. Regards, Tom

I'm curious as to why the code doesn't reflect this. Seems like it would be important to impose a 1/2" per foot maximum to reduce the chances of these kind of flow issues. Thanks again!