San T vs Wye

[KeithThirgood]

I am confused about SanTs and Wyes. I understand SanTs cannot be used on their backs, so they cannot be used to connect a vertical drain to a horizontal drain pipe. For this, a wye plus 45-degree elbow must be used.

Where my confusion lies is with connecting a horizontal drain pipe, into a vertical stack. I have read on some sites that a Wye with a 45-degree elbow must be used but on another site, it says that a wye and 45-degree elbow is prohibited and that a SanT must be used. I have looked at the Ontario Building code online, but I have not been able to find clarity there.

Extra info, which may or may not be relevant. There are other fixtures coming into the stack on the floor above.

 

[Terry]

If you are installing a trap arm to a vertical, with the lower part being waste, and the upper part the vent, then a santee.
If you have waste from a floor above, it's a waste stack. You're not using the upper part as a vent. You can use either the santee or the wye.

 

[Sponsor]

 

[hj]

An "unvented" waste arm into a vertical pipe MUST use a sanitary tee, UNLESS there is another arm coming in to the other side, in which case you use a "back to back fixture fitting". Otherwise you can use either a sanitary tee, a combination Y-1/8 bend, or a Y and 1/8 bend.

 

[Stuff]

How do the codes apply to a toilet drain? Not quite the same but there was another thread where someone's inspector didn't allow a wye.

 

[hj]

The toilet arm is typically, NOT vented, and an inspector going by the "letter of the code" would reject, even though that means he is ignoring the REAL dynamics of a toilet flush.