Wet vent vs. Dry vent UPC question

[puddi]

Hi I'm in California, and Sec. 905.2 says that a vent pipe connecting to a horizontal waste pipe must have its entry point above the centerline of the waste pipe.

However.. there's no such requirement for a connecting waste pipe.

So, what if the connecting pipe is a wet vent? If it's treated like a waste pipe, then what's the point of having the above-centerline requirement for the dry vent, only to waive it for the wet vent?

The actual situation is that I'm venting a waste trap located between floor joists and the vent pipe has to pass through a joist, and if the angle of attachment were above the centerline of the waste pipe, the hole couldn't be placed within the center third of the joist. Can I game this by using the vent as a wet vent? That seems bizarre.

 

[Reach4]

So, what if the connecting pipe is a wet vent? If it's treated like a waste pipe, then what's the point of having the above-centerline requirement for the dry vent, only to waive it for the wet vent?

Solids that get into the wet vent pipe can be washed out by the lavatory (etc) drainage.

 

[Sponsor]

 

[puddi]

Solids that get into the wet vent pipe can be washed out by the lavatory (etc) drainage.

Thanks, that makes sense. I thought the above-centerline requirement had something to do with the free entry of vent air being hindered by the water level in the drain pipe.

 

[Tuttles Revenge]

Also... not all codes make sense or have they been engineered. Sometimes it was just a great sounding idea and its just carried over forever.

Like a 2" vent for a toilet can NOT have any dips or obstruction that reduce its size or a toilet won't work right? unless its in an IPC county.. or if that vent carries the waste from an upstream sink that is now taking up 1/3 of its horizontally laid vent.. But how can a horizontal vent possibly work under the flood level of the fixture unless you're in a UPC county? Boggling.