Venting question: sanitary tee vs wye + 45

[Waterdog]

Hi all,

My question is:

Is there an advantage or disadvantage to using a sanitary tee over a wye + 45 vertically for drain/venting purposes? Do wye + 45 fitting have any purpose in a stack application?

I checked the forums and have never seen this discussed.

I know sanitary tees are never to be used on their side because of flow restriction or in place of a combo wye. However, I have never seen anything about using a combo wye in place of a sanitary tee in a vertical application or for drain/venting.

Thank you for insight.

 

[Terry]

It's been discussed.

If you have venting a lav, shower or tub, the combo or wye with 45 is used on the horizontal.
Coming off the vertical, it's a santee.
A wye fitting on the vertical creates an S trap that siphons. The wye can be used on the horizontal, and is now required in case someone later uses that as a drain, (wet vent).

 

[Sponsor]

 

[hj]

IF the fixture has a vent between the trap and the stack, then you can use any fitting you want to, as long as it is a "drain fitting".

 

[Waterdog]

Ahh I see thanks for the responses. Where I am hung up is how it creates an S-Trap. Maybe because it drains to well and fast with the extra curvature, whereas with a san-tee it just kinda dumps into the stack?

I was looking at plumbing and saw a wye with 1/8 and instead of a San tee on a main stack and when I asked someone about it they said it was as good if not better because the extra curvature helps it drain. I suppose it helps it drain so well it could make it an S-trap and can have the risk of siphoning. In this case the other end of the pipe connects to a washer vented with an AAV.

 

[Terry]

We also have distance to deal with. The vent comes in "before" the trap arm angles too low. The bend on the combo or wye fitting prevents that venting. Oh yeah, it pulls water real well when you are siphoning, but then the water seal is gone too. If the water seal is gone, then you have an open line to the sewer.

Doesn't sound like the person you asked was a licensed plumber if he didn't know that.

Helpful Plumbing Hints for Residential Construction by Bert Polk Plumbing Inspector Lincoln County

 

[Grizzle84]

We also have distance to deal with. The vent comes in "before" the trap arm angles too low. The bend on the combo or wye fitting prevents that venting. Oh yeah, it pulls water real well when you are siphoning, but then the water seal is gone too. If the water seal is gone, then you have an open line to the sewer.

Doesn't sound like the person you asked was a licensed plumber if he didn't know that.

Helpful Plumbing Hints for Residential Construction by Bert Polk Plumbing Inspector Lincoln County

So if i have a 90 coming from toilet flange to main line horizontal and want to vent to the side but up to vertical (so basically i'll have have a 4x4x2 but at an angle so it doesn't catch any water) it ll be facing angle, connect with 45 to a vertical 2" pipe to roof, i was thinking of using the wye but i should use a sanitee??