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Thread: Sanitary Tee on it's back

  1. #1
    DIY Junior Member edtuck's Avatar
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    Default Sanitary Tee on it's back and what else is wrong

    So, I am trying to tie into this existing plumbing, and I realize some things are not done right. So the 3in combo shown in the picture is a toilet with a clean out. The toilet is vented by a sanitary tee with a 2 in branch at a 45degree angle to avoid a joist. (is the sanitary tee on it's back ok as a vent?) This 3in line does a couple 1/8 bends to avoid a footing and then ties into a wye at the main. The wye is connected to a 3in sanitary tee which is in a fernco fitting (bushing?) to tie into the main. The vertical is a vent because the toilet used to be connected at this point. On the other branch of the wye we have a tub and vent (off frame camera left) which goes through a combo on it's side with a cleanout and then receives waste from a sink. Here is where the obvious trouble begins. Two sanitary tees on their backs! The first is connected to an old vent and the second is waste from a double sink. I know, I know, a sanitary tee is not allowed on it's back... but... the waste one is right against all of the 3in ABS fittings that tie into the old cast iron and they are all so close that it would all have to be ripped out to get rid of the t. However, the other sanitary tee can be replace by a combo. With the addition I am doing, the combo will be receiving waste from 4 sinks. I would then put a cleanout on the branch of the second sanitary t, so it is kind of like a double cleanout, but with a sanitary tee. Is this ok, or is an inspector going to freak out? Basically, can a sanitary tee be on it's back if the branch is a cleanout?

    I have also attached my remodel idea to add a tub and shower on the branch that currently has just a toilet in the existing bath. I would add a horizontal combo where the toilet clean out is and put a new cleanout on the combo. All bends shown are combos and all waste is entering the system through a combo as well.

    So, does it sound like this is all going to be to code and Ok, if I make these changes? Sorry it's so much info. Thanks a lot for your replies! Reading this forum has already taught me so much. BTW the picture on the right is looking the same direction as the drawing and the picture on the left is looking from the opposite POV. Oh, and all vents are drawn in Grey.
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    Last edited by edtuck; 05-27-2012 at 10:27 PM.

  2. #2
    DIY Member dw85745's Avatar
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    (is the sanitary tee on it's back ok as a vent?)
    IMHO Yes, -- but only for dry venting. Can NOT be a Wet Vent or for ANY drainage.

    Add: Look at the bottom Note which supports SAN-TEE use for venting. https://ibcode.com/uploads/Aug_24_Sanitary_Tee.pdf
    The bottom pictures show waste into SAN-TEE and I agree use for waste is NOT TO CODE.

  3. #3
    In the Trades Tom Sawyer's Avatar
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    I don't know why this San-Tee issue is so hard to comprehend. A sanitary tee laid horizontally, where the run is used to convey waste is prohibited because the fitting does not direct the flow properly. In other words when the solids and such come down the pipe they hit and splash on the bottom of the fittings instead of being directed downstream. Eventually this can cause a blockage to occur there. You absolutely can however, lay a san-tee on its back and use the run for venting only, no waste allowed. Drain cleaner guys however will hate you because it can make rodding the drain a pita.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  4. #4
    Test, Don't Guess! cacher_chick's Avatar
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    Here is a nice link to Bert Polk's plumbing tips (http://www.co.lincoln.or.us/planning...mbingguide.pdf)

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    DIY Junior Member edtuck's Avatar
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    Default Ok, got it, what about the rest of my diagram?

    Great, thanks! I knew those sanitary tees were a problem, just didn't have any reference saying they were ok on their back as vents. I figured they were, but didn't have the reference so thank you for that, dw85745. Cacher-chick, Bert Polk's plumbing tips is a great pdf file. I have refered to it numerous times in the past weeks trying to plan out all of this new plumbing. The pictures are great and I even used them in another post to clarify my intentions for use of a double fixture fitting.

    So, does anyone see anything wrong with the rest of my diagram? Tub upstream from toilet, etc. On another note, thanks for that article DW85745, I had forgotten that combos and wyes should not be used vertically to connect to venting. It seems however, that a double sanitary tee should not be used for back to back sinks, nor a double combo or double wye, but a double fixture fitting is the only fitting that may be used. Right? Thanks again for the speedy replies everyone, this input is great!

  6. #6
    In the Trades Tom Sawyer's Avatar
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    A double fitting is the "preferred" fitting but is not always a requirement. Check with your local inspector. Around here, nobody uses double fitting's Mostly because none of the supply houses carry them.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  7. #7
    DIY Junior Member edtuck's Avatar
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    Now I see another issue! I just realized that my new tub and toilet (red box) are joining the existing toilet before it is vented. I was going to connect them to the cleanout of the combo that is receiving waste from the existing toilet. Is this ok? Allowing other fixtures to join a toilet before its vent?

  8. #8
    DIY Junior Member edtuck's Avatar
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    Wow, that's a quick reply, thanks, TOM! My local Lowe's (Los Angeles County) actually has double fixture fittings, so I've picked up a couple of them already.

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