Horizontal Vents Design Question: Can I continue existing design?

[Corona_made_me_do_it]

Experts,

First I wan to thank you for the wealth of knowledge you offer in this forum. It has been a tremendous help and given me the confidence to take on my bathroom job on my own.

Situation:

• Bathroom Reconfiguration - Moving Toilet Across the Room
• Existing design has a horizontal (dry) vent. same plane as drain plumbing, no fixture before vent. I did find some residue in the horizontal vent closest to the toilet, but i wasn't too bad.
• 14 year old construction , Dallas TX.

Design Question: Can I continue with this design? If so what precautions should i consider? increased slope or clean outs? or should i reroute the tub drain to the dry vent in question and make it wet vent? I'm worried that this will affect vent capacity for the entire system.

 

[Corona_made_me_do_it]

Bump to see if i can get anyone to chime in here.

 

[Sponsor]

 

[wwhitney]

I think your diagram is hard to follow. Perhaps it would help if you had separate before and proposed diagrams. But ultimately it may be difficult to convey all the information required on a 2-D plan view diagram.

Cheers, Wayne

 

[Corona_made_me_do_it]

I'm not sure what the 3rd dimension would add everything in questions is on the same plane. I can mock up a side view though.

 

[Corona_made_me_do_it]

I don't have a 3d modeling software, but here are my options. Original question is can i dry vent the toilet horizontally like it was done in the original construction.

 

[Corona_made_me_do_it]

If the horizontal dry vent is not allowed. (i've heard it both ways so now I'm confused) would either of these options be a better choice.

Option 2: gives me a 2" wet vent, but is farther from the toilet
Option 3: gives me a wet vent that is within 6', but is only 1.5 "

 

[wwhitney]

My understanding is that you can dry vent a 3" horizontal toilet drain within a floor joist system by using a 3x3x2 wye, rolled up 45 degrees above flat, and then turning horizontal with one or two fractional bends (depending on the direction you wan to run). Then when you get underneath a nearby wall, use a long turn 90 to rise into the wall.

If you are crossing sawn floor joists, holes are limited in diameter to 1/3 of the joist height, and you need to leave 2" of solid wood at the top and bottom of the joist. So it can be very challenging to make it all work in the limited vertical space.

Having the vent run horizonal below the flood rim level of the fixture is only allowed when structural obstructions prohibit any alternative path, such as this case. And then you have to use drainage fittings below the flood rim level, hence the long turn 90.

Cheers, Wayne

 

[Corona_made_me_do_it]

Thanks. I have floor truss joists so i have room to get through them, but not a lot of room above the 3" drain to go up 45 degrees.

 

[wwhitney]

So then you have two options:

1) Lower all the 3" drains so that your dry vent can come off and minimally rise before going horizontal, while still fitting within the floor trusses. Note that if you take off the vent farther downstream, you'll have more height above the 3" horizontal drain.

I believe if you are under the IPC, the vent takeoff for the toilet can be arbitrarily far downstream of the toilet, as long as it is before the toilet fixture drain combines with any other drain. Under the UPC, there's a limit to the toilet fixture drain length before the vent, I think it may be 6'.

2) Wet vent the toilet.

Cheers, Wayne

 

[Corona_made_me_do_it]

Thanks wwhitney. I think I'm going to just wet vent the toilet by taping in the tub drain or the vanity drain/vent.

IPC/UPC aside do you know which fixture would be best to tap into for the wet vent? The tub has a 2" vent, but is about 70" away while the vanity is 3 or 4' away, but only has the 1.5" vent. Might not matter too much but I'd like to be correct and the work is pretty similar for both options.

 

[wwhitney]

The toilet requires a 2" vent. I think option 2 is what you want, assuming I follow your diagrams correctly (not sure that I do).

Option 3 doesn't make any sense to me, as it looks like you are just connecting two different horizontal drain lines with a cross-connect. A wet vent is a single pipe that is both a vent for one fixture and a drain for another.

I believe the reason that a flat dry vent is prohibited is that solids can accumulate at the flat vent takeoff and potentially obstruct it. Whereas with a wet vent, that vent takeoff is also a drain for a fixture, so the drainage from it will provide some flow to keep that from happening.

Cheers, Wayne

 

[Corona_made_me_do_it]

Thanks Again option 2 makes sense to me and I already have it dry fitted.

I would like to better understand how the vanity would not vent the system at some point, but for now I better just move on

Thank You again for taking the time to assist and dealing with my bad diagram.