Sanitary Tee Upside down for venting?

[Markos]

Hi Pros,

I’m a bit confused as to whether a sanitary tee should or should not be “upside down” when used for horizontal-to-vertical transitions above the flood plane. I have approved old work that is configured with an upside down tree. I’m wondering if I need to flip line before gluing up the new stuff.

 

[wwhitney]

Put it in upside down. It's conventional, even though it doesn't matter and the other way isn't a code violation.

Cheers, Wayne

 

[Sponsor]

 

[hj]

It is a violation here.

 

[wwhitney]

It is a violation here.

What code section is referenced?

Thanks,
Wayne

 

[Markos]

Thank you!! My preference is not upside down. I understand that in theory they could flow air better upside down. Seem negligible through. I’m dry fit for right side up so as long as it meets code I may go that way.

 

[Tuttles Revenge]

If you're in Seattle/King Co metro area it will fail if its not in the correct orientation of air flowing out or condensate dripping down.

It will be argued that the downward sweep of a San Tee restricts the size of the vent on the invert side of the vent reducing its overall size.

Its entirely possible that the inspector won't care, or won't notice.

 

[wwhitney]

It will be argued that the downward sweep of a San Tee restricts the size of the vent on the invert side of the vent reducing its overall size.

Is there a UPC reference that goes along with that? Otherwise that sounds 100% bogus.

But perusing UPC Chapter 9, I do see:

905.1 Grade
Vent and branch vent pipes shall be free from drops or sags, and each such vent shall be level or shall be so graded and connected as to drip back by gravity to the drainage pipe it serves.

So if an inspector wants to be unreasonably persnickety, they could argue that in the drainage configuration (aka right side up), the short inside radius of the branch of the san-tee would constitute a section of vent that is graded so as to drip back by gravity to a different drainage pipe than the drainage pipe that the vent serves.

However, I would argue that "each such vent" refers to "vent and branch vent pipes" and hence does not cover fittings.

Cheers, Wayne

 

[wwhitney]

My preference is not upside down.

If your preference is aesthetic, rather than performance based, it doesn't matter.

"Upside down" is clearly conventional and runs no risk of getting a correction (justified or not). "Not upside down" has no upside that I'm aware of. Go with "upside down."

Cheers, Wayne

 

[Tuttles Revenge]

Is there a UPC reference that goes along with that? Otherwise that sounds 100% bogus.

But perusing UPC Chapter 9, I do see:

905.1 Grade
Vent and branch vent pipes shall be free from drops or sags, and each such vent shall be level or shall be so graded and connected as to drip back by gravity to the drainage pipe it serves.

So if an inspector wants to be unreasonably persnickety, they could argue that in the drainage configuration (aka right side up), the short inside radius of the branch of the san-tee would constitute a section of vent that is graded so as to drip back by gravity to a different drainage pipe than the drainage pipe that the vent serves.

However, I would argue that "each such vent" refers to "vent and branch vent pipes" and hence does not cover fittings.

Cheers, Wayne

I 100% agree that its bogus. Especially since venting can be engineered with vastly smaller sized pipe than the minimum called for by the chart. I think its more of if you do it the "wrong" way we know you're a Newb mentality.

We always install vent san tees in the "correct" orientation and never have this conversation with our inspectors.

 

[Reach4]

"Not upside down" has no upside that I'm aware of. Go with "upside down."

I think OP is saying that the santiary tee fits better inverted. That implies that the end hubs are not symmetrical around the side hub. I did not look into the dimensions to verify one way or another.

 

[wwhitney]

I’m wondering if I need to flip line before gluing up the new stuff.

If you have a dry fit mockup, note that plastic DWV is an interference fit. Therefore if you glue up each joint and press it home as is best practice, your fittings will move, as the pipe will go deeper into the socket.

So expect to recut some of your pipes 1/4" - 3/4" longer if you want to keep the fittings where you have them in your dry fit mockup. When doing that, you should be able to accommodate the changes in pipe length necessary to flip your vent san-tee to the conventional "upside down" orientation.

Cheers, Wayne

 

[Markos]

If you have a dry fit mockup, note that plastic DWV is an interference fit. Therefore if you glue up each joint and press it home as is best practice, your fittings will move, as the pipe will go deeper into the socket.

So expect to recut some of your pipes 1/4" - 3/4" longer if you want to keep the fittings where you have them in your dry fit mockup. When doing that, you should be able to accommodate the changes in pipe length necessary to flip your vent san-tee to the conventional "upside down" orientation.

Cheers, Wayne

Oh I’ve had to recut just about everything on the drain side. Especially the 3”, which resulted in some geometry changes also. The 2” dry fits pretty well with minimal change since the flange isn’t that deep. Not a lot of waste though because the pieces that I remove end up getting used as I progress through gluing.

 

[Markos]

I think OP is saying that the santiary tee fits better inverted. That implies that the end hubs are not symmetrical around the side hub. I did not look into the dimensions to verify one way or another.

Yeah sanitary tees are not symmetrical. So since I dry fit in the draining water orientation then the horizontal pipes are a bit off. As mentioned however I’ll need to recut most of my runs anyway since the glue causes the pipes to seat better.

If your preference is aesthetic, rather than performance based, it doesn't matter.

"Upside down" is clearly conventional and runs no risk of getting a correction (justified or not). "Not upside down" has no upside that I'm aware of. Go with "upside down."

Cheers, Wayne

I am skeptical of the performance benefits. This isn’t an intake manifold on an internal combustion engine. Air is going to flow through the tire regardless of the orientation of the curve. I will heed your advice and orient them upside down however.