DWV Sanitary Tee question

[baldmagicguy]

Greetings! I'm hoping one of you Master Plumbers out there can answer a question for me.

I'm going through the code book and I understand that it's a no-no to put a sanitary tee on its back. I can understand why this is forbidden if the vertical connection is a drain. A combo would be the solution for that scenario.

What a don't understand (and maybe my understanding is flawed) is why can't you use a sanitary tee on it's back if the vertical connection is a vent? This would be a crown vent, right? And a crown vent, as long as it's more than 2 pipe size diameters away from a trap, is allowed... am I still correct?

Thanks in advance for sharing your vast knowledge.

Regards,
Marty

[hj]

A crown vent comes off the inverted U bend of an "S" trap and is NEVER permitted. The codes SPECIFY that any fitting below the overflow level of a fixture MUST be assumed to be a drain fitting, not a vent fitting, because it will fill with water when the line is obstructed. In this case you are trying to be logical and the codes are not necessarily logical.

[baldmagicguy]

A crown vent comes off the inverted U bend of an "S" trap and is NEVER permitted. The codes SPECIFY that any fitting below the overflow level of a fixture MUST be assumed to be a drain fitting, not a vent fitting, because it will fill with water when the line is obstructed. In this case you are trying to be logical and the codes are not necessarily logical.

hj,

Thanks for the reply. LOL! I drive my wife nuts all the time by being logical. I was reading through the code book trying to make sense of some of the rules. Just doing this has increased my respect for plumbers tenfold. You guys really have your work cut out for you.

Thanks for the explanation. I was wondering what evil might be lurking by putting a sanitary tee on its back.

Regards,
Marty

[Terry]

I was wondering what evil might be lurking by putting a sanitary tee on its back.

One explanation I heard was
Someone may come by later and use a vent for a waste line, so anything below grade must be run with waste, and not vent fittings.

Of course in plumbing, ask ten inspectors and you will get a variety of answers. Most pretty close.

[nhmaster]

IPC allows a san tee to be used for vertical venting as long as it is dry.

[Terry]

IPC allows a san tee to be used for vertical venting as long as it is dry.

UPC requires the use of a santee if it's vertical.

[hj]

A sanitary tee is cheaper than a combination Y-1/8 bend, that is why the IPC allows it. Many things in the code anticipate future actions, which is why the horizontal run or connection of an individual vent has to be at least 42" above the floor. In case a 36" kitchen sink is eventually connected to it and thus the 6" above the rim will be maintained.

[nhmaster]

HJ, are you saying that the IPC guys were bought off by the manufacturers

[hj]

NO, the contractors. The UPC and IPC had a merger agreement, but when the IPC contractors learned that they would have to go back to doing good plumbing, they tore up the agreement.

[patrick88]

NO, the contractors. The UPC and IPC had a merger agreement, but when the IPC contractors learned that they would have to go back to doing good plumbing, they tore up the agreement.

LOL That is too funny