We want to install a bathroom on our 2nd floor. Our house is built on a slab and we have a septic system. The bathroom we want to install would be directly over a 1/2 bath on the 1st floor. Is it possible for these two toilets to share the plumbing that goes out to the septic tank? Can you just run plumbing down the wall to the 1st floor toilet?

Do you have a vent pipe coming up inside the back wall of the bathroom? The vent pipe would continue through the attic and out through the roof.

Yes, we do have a vent pipe.

Hey HD... check out the attachment below (click on it)

When you answered Ballenger's question... is there vent in wall? You answered yes. Can you tell me if two inch pipe or 3 inch vent pipe..

Anyway, most 1/2 bathrooms have a 2" vent that wet vents the toilet as well as the lavatory..so I am assuming you only have a 2" vent there.

In my first pic. (on left) I drew a typical 1/2 bath plumbing diagram.

In the second pic (on right) I drew the typical 1/2 bath on 1st floorand what usually needs to be done to add a bathroom to the 2nd floor. Here, will need to open the bathroom floor and connect into the 3" or 4" drain pipe underground AFTER the 1/2 bath sink drain has been installed (see pic.).

then will need to run that 3" vertical and pick up waste lines to the toilet, tub, and lavatory.

Piping diagram will change depending on location of fixtures, but basically you want to use the tub or the lavatory vent to wet vent the toilet and then connect vents together and then run 2" vent trhough roof or tie vent into vents in attic space.

At diagram you will see:

VTR = vent through roof (or can also go to attic vents).

Dandy clean out (required at the base of any waste stack)

Now...this is only a preliminary start for you. best thing is to open wall and take a picture so we can really tell you what is going on here!!

And, to answer question... YES you can connect both bathrooms together and drain into septic!

Let us know what you think.

If this answer helped please RATE THIS ANSWER. Thank you... Mark

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