Two on a stack....

[mrcaptainbob]

Is it permissable to have two toilets (1st flr and 2nd flr) flush to the same stack? My son and I were discussing this and he spoke of a possible issue with venting. I checked the situation in my house and the two pipes (one directly from the 1st flr toilet) are connected to an horizontal wye, then to the septic tank. Of coarse the vent stack continues in size through to the roof and is intercepted by the 2nd flr toilet.

[LazyPup]

When two or more unvented fixture arms are connected to a vertical stack the section of line from the base of the stack to the uppermost fixture is classified as a "Combined Waste & Vent." We may not connect an unvented fixture arm to a combined waste and vent below a watercloset fixture arm.

Please refer to the attached illustration:

In Figure A even though both water closets are effectively vented by the vertical vent stack nonetheless water closet # 1 is attached to the drain line while Water Closet #2 is attached to the stack thus it would meet code approval.

In Fig.2 both waterclosets are connected to the vertical stack. In this configuration water closet number 2 would be a violation because we may not connect an unvented fixture arm to a vertical stack below a water closet.

[mrcaptainbob]

Two on a stack issues....

Thanks, LazyPup. Since what I have matches figure 1, it's comforting to know SOMEthing in this old house matches code!