Vent Tees for venting horizontal branch drains

[Mliu]

It's my understanding that a Vent Tee can be used on its back to dry vent a horizontal branch drain. But when looking at diagrams and photos of horizontal branch drains, the majority show the installation of a Sanitary Tee on its back for connecting the dry vent. I believe both tees are acceptable, but I'm wondering why there are so few examples of Vent Tees being used.

Is it because of a mistaken belief that all tees in DWV piping must be Sanitary Tees?

Is it because people think that a Vent Tee can only be installed in vertical dry vents? (Btw, I see more Sanitary Tees than Vent Tees used in vertical dry vent piping too.)

Or is simply to cut down on the number of parts a plumber has to keep in inventory (since a Sanitary Tee can be used anywhere a Vent Tee can be used)?

 

[Terry]

I have never seen any plumber use a vent tee before. I had to google it and I've been plumbing since 1973.

My inspectors want to see a wye or combo if you're venting horizontal on it's back.
Santee on the vertical.

 

[Sponsor]

 

[Mliu]

My inspectors want to see a wye or combo if you're venting horizontal on it's back.
Santee on the vertical.

Can you explain the rational (and code) behind this?

I understand the reason for a wye or combo on its back where a waste or soil stack meets a horizontal branch drain; otherwise, the falling sewage dropping straight down can create a blockage to the upstream horizontal pipe. But a dry vent obviously doesn't cause that problem. There is no logical reason (and, as far as I know, no regulatory reason) to require a wye or combo. These should be acceptable:

In the IPC, the only vent connection restriction I'm aware of is the following:

905.3 Vent Connection to a drainage system.
Every dry vent connecting to a horizontal drain shall connect above the centerline of the horizontal drain pipe.​

I can only think that some inspectors (and probably some plumbers, too) have taken the hard rule of "No SaniTee on it's back for vertical waste connections" (e.g., IPC Section 706.3) and mistakenly applied that to ALL vertical pipe connections, including dry vents.

 

[Terry]

Then do it your way, pull a permit and have it inspected.
The reasons for the wye fittings according to my inspectors is that sometime in the future as part of a remodel it "will" be used as a waste line. They are looking forward.
I give advice here that is meant to help anyone pass an inspection on their first try regardless of where they are from.
But yes, plumb it how you like, get your inspection and let us know how that goes.

 

[Terry]

Dream Home Cosultants, have they ever plumbed a home? 2011? Seriously?

 

[Terry]

Carson Dunlap home inspection.
Not plumbers, but Geeze, anybody can plumb. Just ask the guy at Home Depot if you have a question. These are your sources?

 

[Mliu]

Then do it your way, pull a permit and have it inspected.
The reasons for the wye fittings according to my inspectors is that sometime in the future as part of a remodel it "will" be used as a waste line. They are looking forward.
I give advice here that is meant to help anyone pass an inspection on their first try regardless of where they are from.
But yes, plumb it how you like, get your inspection and let us know how that goes.

Terry, I did not intend to suggest that you were doing anything wrong or that you aren't familiar with the codes. After re-reading my post, I can see it may have come across that way. For that, I sincerely apologize. What I was trying to say is that people, not anyone specific, sometimes do what they think is the correct way or what they were taught is the correct way, even though it may not be required. I also understand that, if inspectors want it done a certain way, it's often easier and involves less headaches to do it that way than not to.

 

[Mliu]

Carson Dunlap home inspection.
Not plumbers, but Geeze, anybody can plumb. Just ask the guy at Home Depot if you have a question. These are your sources?

Carson Dunlap home inspection.
Not plumbers, but Geeze, anybody can plumb. Just ask the guy at Home Depot if you have a question. These are your sources?

No, these are not my sources. Those were just a couple of example pictures from a quick internet search. My ultimate sources are the code books, which is why I always ask for code references when I ask these questions. I'm not as familiar with the UPC, but I have found nothing in the IPC that requires Wyes or Combos for vent connections. The only restriction I could find is the one I quoted above. But I don't claim to be an expert. And often, the codes are not quite as clear as they could be, so then there's the matter of professional interpretation. Which is why I am seeking advice here.

Again, I apologize for sounding like I was challenging your expertise. That was not my intention at all. I greatly appreciate the forum you provide here and your personal contributions of knowledge and experience.

 

[Terry]

In the 70's I was still using vent 90 fittings and then I realized that a medium 90 cost less and I could use them in more places. A typical home would use 20 of them. I would install 100 per week and I quit using the "vent" 90 fittings that were kind of useless anyway. It made for a better job too.

 

[MACPLUMB]

The reason is you always want to have a natural slope to drain piping, so rain water running down vent will flow, and also because
many times Plumbers/Drain people will snake down a vent pipe so you want it to go down the drain and "NOT" back toward the fixtures