jeck

I am adding an upstairs master bath in a small room connected to the master bedroom. There is a wet-wall containing plumbing for an existing upstairs bath and existing downstairs bath. The existing upstairs and downstairs toilets each have their own wastepipes to the main drain in the crawlspace. Can a new toilet connection be added to the vented vertical wastewater pipe that serves the downstaires toilet or would this be a no-no? If not, can a 2-way toilet arrangement (one on each side of the wet-wall) be installed on the vented upstairs vertical wastepipe?

Nestor_Kelebay

I'd contact my local plumbing inspector to find out what's required in San Diego.

In my building I have three toilets (one on each floor) in an apartment building all discharging into the same stack. For example, the toilet in suite 3, suite 10 and suite 18 all discharge into the same vertical cast iron pipe.

However, if your house was built with each toilet discharging into it's own stack, then there's a difference in what the plumbing code requires where you live. And you have to go by your local rules.

majakdragon

As Nestor said, check with your code office. I am guessing that the reason your existing toilets have seperate stacks is because they are not above each other. Cutting out wall studs/ceiling joists to connect piping horizontally to one stack was probably not an option.

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Redwood

What I'm reading is the upstairs bath waste pipe is separate from the vent of the downstairs bath. If this is the case it is okay to add. Waste cannot dump into the vent of the downstairs bath as wet venting between floors is not pemitted.