Hi all, we are looking into the possibility of adding a second toilet in the upper floor of our house. The new toilet would be installed about 5 feet from the old toilet in the master closet. In the closet there is already plumbing for a sink (hot/cold water and drain). Is it possible to connect this new toilets drain to the existing toilet, will it need a vent, etc...
Thanks in advance for your response.

Trekmicro.

Five feet is max you can go from soil stack; you don't want to share the drains between two toilets. Each should have their own pipe attached at soil stack. Otherwise when flushing, the pressure will push water up and perhaps even waste into second toilet.

Five feet is max you can go from soil stack; you don’t want to share the drains between two toilets. Each should have their own pipe attached at soil stack. Otherwise when flushing, the pressure will push water up and perhaps even waste into second toilet.
I disagree. We have installed many units with two bathroom groups using the same 3" branch to get to the vent stack. And you may now increase the distance between vent and ntrap to 10 feet on a 3" drain line.

when flushing, the pressure will push water up and perhaps even waste into second toilet. Again I have to disagree. This can only happen if the branch is clogged downstream from the second toilet.

Is it possible to connect this new toilets drain to the existing toilet, will it need a vent, etc...
If you have a vented lavatory in the closet the toilet will be vented when you run the vent on the new lav. Good luck, Tom

Sorry, code is 6 feet not five. I guess you can connect the 2 with proper connections as speedball1 says, I stand corrected but I have seen outcomes like this one.

https://www.askmehelpdesk.com/plumbing/toilet-empties-when-different-toilet-flushed-31290.html

Venting is crucial; here is national plumbing code for further information.

National Plumbing Codes Handbook - Google Book Search (http://books.google.com/books?id=euDzsOnRxg0C&pg=PA53&lpg=PA53&dq=connecting+two+toilets+to+same+drain&source=web&ots=n_6_O58VOd&sig=sRP5XVbTJp_Nsbl6EBkuIpYfZsU#PPA51,M1)

Update your codes. Paste "Plumbing Code distance between trap and vent" up oin your search bar and read the different distances between trap and vent. On different codes. For example while UPC gives us 3" at 6 feet and 4" at 10" IPC and Magraw-Hills Plumbers and Pipe fitters Calculating Manual gives us 3' at 12' and 4' at 16 feet.. It all depends upon what code you're working under. Regards, Toim

They are not my codes, I don't think I like your attitude speedball. I am simply trying to help someone eliminate a problem by thinking and avoiding further problems.

The National Plumbing code I posted explains the 3”&4” rule, try reading it. Post something useful and not combative, oh I guess you only do that for $.95 a min on your pay advice number listed by your name……

What is the best way to plumb the new toilet into the old one, can we do a Y on the horizontal pipe or do we need to do it on the vertical pipe in the wall? From reading the previous posts I think that you are saying that I can use the vent from the lav for the toilet, it this right?

TREKMICRO... if there is enough room for you to roll a 3 x 2 wye fitting above centerline of the waste line (and still be able to turn up to the toilet with a street 90 and a flange) then you can use the horizontal pipe with a 3" wye to pickup toilet AND you can use the 3x2 wye (rolled above centerline) just behind the toilet fitting to pipe 2" pipe to lavatory... acting as a wet vent for toilet AND an individual vent for the lavatory.

If not... you will need to tie into the vertical... TRY it out with fittings in hand.. open floor.. see what happens. GOOD LUCK and let us know how it works out!!