Sanitary Tee or Wye under toilet flange

[Trey]

I've come across some conflicting info about having sanitary tees or wyes vertically installed under toilets where a wet vent joins in. I know generally you'd use a tee since it's a horizontal to vertical joint, but I've also come across advice that a wye is better directly under a flange because it helps it prevent horizontal venting below the foundation slab.

Thankful for any input!

 

[Reach4]

Both are acceptable. Wye is a little better. For showers or other drains, you need to pass air to break the siphon; for those you need the sanitary tee. Toilets are different. They siphon on purpose. The trap is in the toilet, and gets refilled by the little hose down that squirts water down the overflow.

 

[Sponsor]

 

[Terry]

A toilet can be vented with a wye or a santee. The bowl is designed to siphon and then gets refilled by water in the tank.
Every other fixture in the home has a p-trap that is designed to not to siphon out. Those get vented the normal way.

 

[Trey]

Thank you both! As a follow up question, does it matter if I use a 4 inch flange and tee that changes to a 3 inch pipe (using a 4x3 closet elbow) or should I just make it 3 inch all the way? I don't want the size reduction to induce clogs but I figured at that size it wouldn't hurt anything.

 

[Terry]

Most toilets have a 2" trapway. In what way will a 3" restrict flow?

 

[Trey]

I know the general principle is to try and not reduce the size of the pipe downstream. If I install a 4" pipe under the flange through the tee then reduce it to a 3" pipe underneath I wanted to make sure that wouldn't cause any issues. But since it originates from a 2" trapway in the toilet I guess that answers my question

 

[Reach4]

The thing that you may want is called a 4x3 Closet Bend. 4 inch where the flange connects and 3 inch on the output.

With 4 inch up top, there are various choices, some of which are no-glue, for those of us that may not do things right the first time.

https://terrylove.com/forums/index.php?threads/4x3-closet-bend-vs-3-long-sweep.68679/
https://terrylove.com/forums/index.php?threads/4-x3-closet-elbow-too-low-on-remodel.79072/

 

[Gabriel1989]

Both are acceptable. Wye is a little better. For showers or other drains, you need to pass air to break the siphon; for those you need the sanitary tee. Toilets are different. They siphon on purpose. The trap is in the toilet, and gets refilled by the little hose down that squirts water down the overflow.

Please I’ve same situation, please indicate if this installation is good

 

[Gabriel1989]

Please I’ve same situation, please indicate if this installation is good

 

[Gabriel1989]

I've come across some conflicting info about having sanitary tees or wyes vertically installed under toilets where a wet vent joins in. I know generally you'd use a tee since it's a horizontal to vertical joint, but I've also come across advice that a wye is better directly under a flange because it helps it prevent horizontal venting below the foundation slab.

Thankful for any input!

Please I’ve same situation, please indicate if this installation is good