DWV Venting question

[hd54kh]

Hi all, Maybe a quick question about venting. I have a horizontal 3" main drain in a crawl space that I need to add to and change a sanitary T to a 45. I am moving a toilet, sink and shower and was not the best venting to begin with. Does it matter if the new venting exhausts thru the side or does it need to be vented from the top of the 3" horizontal run. I"ll be working in about an 18" space and the horizontal is lower.

Sawyer

 

[mikegt4]

I am no expert but I would imagine a vent placed anywhere but the top of a pipe would not be code compliant. IIRC, sanitary tee's are required anywhere that carries liquid as an aid to flow. In the vent, which only moves air, a normal 45 is OK. Non solids drains (sink and shower) are allowed a certain lateral distance to a vent, the spec has probably changed since the last time that I had a plumbing inspection for my work (30 years ago).

 

[flat350]

The vent should come off the drain at 45 deg. or more from the horizontal.

 

[billconner]

ditto to flat350.

 

[hd54kh]

Thanks, top venting it is. It is a tight space but I'll have to make it work. I figured the venting would not like material flowing past the opening but I'm not all too experienced at dwv technicalities.

Thanks all firming this up.

Terry

 

[Steve_P]

My house has it off the side. And I can tell you from experience, don't do this! The reasons are obvious.

 

[billconner]

Rolling vent fitting minimum 45 degrees from horizontal should be fine and give a little extra room to work.

 

[brownbagg]

you need it up high just for the odor

 

[hd54kh]

Good info, I figured in my limited venting experience that from the side would make it easy. But from what you all helped me realize is the vent first allows positive pressure ahead of the flow to escape and after the flow passes the vent allows for vacuum release. Probably would work at a side install unless a combination of flows at the same time blocks the venting or the event of a clog would totally block the vent. It'll be a bit more of a challange but I'm going to try my best to do it from the top.

The whole system was installed in that low crawl space about 40' from the access point. I got to repair the area where the bath tub was so maybe when I square the to be replaced area up I'll make it large enough to have my helper cut and pass the pipes/fittings to me from above. Do it once and be done.

I have a good grasp on the routing, length and pitch of the above the floor install but just never found a requirement for the direction of flow.

Thank for all the input.