I am a gc who has had to perform the plumbing portion of some of my projects in order to keep the project rolling along (everyone is swamped). So I am not a professionally trained plumber. My question is this. The inspector flagged me on the combo I used on the toilet saying it needs to be a san tee. I realize a santee is more typical in this spot but my rational for using the combo was that it would shorten the amount of horizontal pipe between the toilet flange and the vertical stack. The inspector said it will not work properly.properly. Is this correct? Is there a code that requires it to be a San tee that he can throw at me if I challenge him. Btw I also realize now that the two other incoming drains (lavatory and Shower would have been better connectednusing 45wye’s instead of the multiple sweeps. If I have to change out the combo, would you pros recommend I switch to the vertical wyes to bring in the other fixture lines too? Thanks in advanceenter image description here

  • The vent inlet is much lower then the closet 90
    – aofkj
    Jul 1 '18 at 14:20
  • Daniel, what you are seeing is the 1.5" lavatory drain coming in on the left and a little of the 2" shower drain coming in on the right. The 3" pipe continues upward above the water closet and reduces to a 2" vent stack. there is no venting coming in below the WC
    – user87228
    Jul 2 '18 at 5:57
  • nevermind Daniel. I see what you are saying...your right! because of the combo, the vent enters in much lower. the san tee will fix this. Is this ultimately why the inspector said it would not work. I have another plumber telling me it will work its just not orthodox.
    – user87228
    Jul 2 '18 at 6:00
  • 1
    That's right because there's no code on water closet prohibiting the vent lower then the drain (trap weir) . It's an exception.
    – aofkj
    Jul 3 '18 at 11:25
  • Wouldn't it actually be impossible for a toilet vent to take off above the weir, since the rim of the toilet bowl is the weir?
    – alexw
    Jun 23 '20 at 17:12

There are a couple of reasons why you cannot connect to a combo, no matter what you are hooking up. No combo can be vertical and tied into due to potential venting issues and the way the water washes away on a vertical combo.

The rule of thumb is you cannot lay a sanitary tee on its side or back and you cannot install a combo in the vertical position. Must be a sanitary tee.

You can connect a toilet to a combo, just not in the vertical position. I am a 20 year licensed plumber in Texas. We have some of the strictest codes and testing in the nation.

  • + for vertical / horizontal explanation.
    – Ed Beal
    Feb 19 '19 at 15:50

I am no plumber either, just been in the construction trade as a supervisor a very long time. One thing I learned is do not piss off the inspector by questioning the items you get cited on, no more than asking their advice on how to fix it to get their approval. If you challenge him or her you will only open up a bag of worms farther down the road. IMO, they do have the upper hand. They usually know the code, it is up to them to enforce it, and if what you are doing is not in the code book, no amount of rational will sway them.

  • Right. Why would they risk the liability, even if the odds are small? Aug 9 '18 at 2:29

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