Plumbing- Multiple Toilets on the same stack

[BigguyZ]

I need a plymber who knows the code to chime in here. I have a friend who is remodeling an old 4-plex, and all of the drain plumbing is going to a single 4 or 5" cast iron stack.

When I bouhgt my duplex, I was told that you can't have the upper lower unit on the same stack. So what is the code? CAn you have more than one toilet on a stack or not? If so, is there a limitation?

Thanks!

[charliex]

Seems to me that at some point all come together anyway. All the waste pipes that I have seen have both floors going to the same stack. Eventually all the waste pipes converge on the main line. Sounds like a plumber is hoping to make a few extra bucks on the pipe and install. If I am wrong please let me know.

Chas

[BigguyZ]

Well, the person who said I needed two stacks wasn't a plumber, but a city inspector...

[JimD]

If the city inspector for your area says you need multiple drains for multiple toilets then I think you know the answer. It doesn't matter what is acceptable elsewhere, if that is what your local code says then it is what you have to do.

If you have multiple toilets on the same 3 or 4 inch (or even larger) stack, and there is a clog, then you lose the drain and vent for all the other toilets and everything else on that stack. They will all get connected together eventually but separating the drains and vents until someplace typically under the house under ground where they all connect helps to minimize the effect of a clog.

Jim

[Uncle Cracker]

If you have multiple toilets on the same 3 or 4 inch (or even larger) stack, and there is a clog, then you lose the drain and vent for all the other toilets and everything else on that stack.

It is at that time when the guilty parties need to learn the intricacies of the incremental flush...

[JimD]

I checked a couple of house design books I consult. One didn't have much, the other one suggested that it is normal to have all the toilets from a house go into one, usually 4 inch, "soil stack". Sinks, tubs, and showers can go into a secondary stack connected to th soil stack at some point.

It also says "consult your local codes". I wonder if the fact that you are dealing with a multi-family dwelling is a factor.

Jim

[toolguy1000]

+1 on jim d's response. there are things that "work" which are acceptable in one municipallity that are unacceptable in another municipality. our city just had it's code modified to accept pvc on above ground DWV, even though surrounding municipalities were permitting it's use for years. whatever your locality stipulates is what you should use.

[woodturner]

Seems to me that at some point all come together anyway.

Sewer, yes, but not the stacks. Unfortunately, plumbing codes have not been nationalized to the degree that electrical and building codes have. Thus, it's harder to tell one the "right way" for their municipality.

From a design standpoint, though, every fixture should separately vent to the exterior of the building. There are some situations in which two fixtures can share a vent, but it's "better" for each fixture to have a separate vent.