Strange fitting, Never saw one B4

[Cass]

I have never seen one of these fittings B4.

It is in the toilet vent. One comes from the kitchen sink the other from the bathroom.

I will post a better pic later today.

[dubldare]

Need a smaller picture, lol.

[dubldare]

Is the upper terminal tapped?

[hj]

The picture is very small, but it appears to be a double tee.

[Cass]

Yes, a double T, I have never seen one piggy backed like this. I will try and get a bigger pic posted.

[hj]

It was not a common fitting, but was useful when you needed one and could find it. They also make one with two tapped openings next to each other.