Toilet Vent Simple Question - 2 floors

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PeterT

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See picture.

Red is current plan, green is proposed.

The 1st floor WC drains into the 3" pipe with a (to be added) 3" to 2" dry vent to roof as indicated.

If I wanted to tie in a 2nd toilet from the floor above, would I have to add a dry vent for the lower WC in the location shown ?

I assume that I can't wet vent the first floor WC through the same 3" pipe that the 2nd floor WC drains into.

thanks.


drain copy_LI.jpg
 

PeterT

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Instead of adding a vent where shown in green, can the lower WC rely on the 2" sink/washer combo drain/vent (labeled sink) for its vent??

The upper WC will have a separate dry vent to roof and the sink/washer drain/vent will tie into vent system in attic.
 
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PeterT

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the downstairs gets vented first.

dwv_b1.jpg
thanks.... to be clear, by " gets vented first" , do you mean the lower WC vent must occur before the lower WC drain ties in to the stack that accepts 2nd floor WC flow?
 

Terry

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thanks.... to be clear, by " gets vented first" , do you mean the lower WC vent must occur before tie-in to the stack that accepts 2nd floor WC flow?

Yes. Otherwise the upstairs flush "pushes" water out of the lower toilet. The venting gives the air a place to go.

dwv_b2.jpg
 
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wwhitney

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In other words, consider the vertical pipes that you have at an elevation of the first floor ceiling. Each pipe can be a drain from upstairs, or a vent from downstairs, but never both.

Cheers, Wayne
 

PeterT

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Yes. Otherwise the upstairs flush "pushes" water out of the lower toilet. The venting gives the air a place to go.

Would a SanT on the vertical waste pipe (labelled "WC" above) be acceptable for the WC 2" vent provided it's tied into the vent system above the WC flood line?
 

wwhitney

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Would a SanT on the vertical waste pipe (labelled "WC" above) be acceptable for the WC 2" vent provided it's tied into the vent system above the WC flood line?
You're talking about a dry vent takeoff between the closet flange and the closet bend? It would need to be a wye, and the dry vent would need to stay vertical (at least 45 degrees above horizontal) until at least 6" above the WC flood line. Then it could go horizontal and/or tie into another dry vent (at least 6" above the flood rims of whatever fixtures it's venting).

So if your closet bend is deep enough that your wye can be deep enough that the vent can get under a wall before rising out of the slab, that would work. From the photo, it doesn't look deep enough.

Cheers, Wayne
 

Reach4

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If you wet vent, under UPC distance from toilet trap to B would be under 5 ft. The lavatory drain could jog to join toilet sooner (farther to the right). Picture is rough. White pipe is new 3 inch ABS, but shown as white for contrast. Orange letters on photo are for discussion.

All fittings for this are 45s, wyes, long sweeps.

So guiding principles, toilet is vented (wet vented in this case by lavatory) before joining other waste. In UPC path is 5 ft or less before vent.
 

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Reach4

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Six ft UPC maximum allowed is going to make it easier.
 

PeterT

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You're talking about a dry vent takeoff between the closet flange and the closet bend? It would need to be a wye, and the dry vent would need to stay vertical (at least 45 degrees above horizontal) until at least 6" above the WC flood line. Then it could go horizontal and/or tie into another dry vent (at least 6" above the flood rims of whatever fixtures it's venting).

So if your closet bend is deep enough that your wye can be deep enough that the vent can get under a wall before rising out of the slab, that would work. From the photo, it doesn't look deep enough.

Cheers, Wayne

Wayne, you're correct... the closet bend isn't low enough to permit a Y to stay vertical to the wall cavity. thanks.
 

PeterT

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If you wet vent, under UPC distance from toilet trap to B would be under 5 ft. The lavatory drain could jog to join toilet sooner (farther to the right). Picture is rough. White pipe is new 3 inch ABS, but shown as white for contrast. Orange letters on photo are for discussion.

All fittings for this are 45s, wyes, long sweeps.

So guiding principles, toilet is vented (wet vented in this case by lavatory) before joining other waste. In UPC path is 5 ft or less before vent.

thanks for the idea, that could work but would require taking up a lot of concrete...so I'm likely going to have to tie in to a different drain in another part of the house unless I can tie in between points E and C on your drawing.

Can I put a 3" san T on its back in that location (between E and C)? or would it have to be a Y?

Then keep the vent at 45 degrees until above flood line.
 

wwhitney

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UPC (California's plumbing code) only allows a san-tee on its back when all the connections are vents. For a 3-way connection with a horizontal drain in and out, you use a wye or a combo.

Cheers, Wayne
 

PeterT

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UPC (California's plumbing code) only allows a san-tee on its back when all the connections are vents. For a 3-way connection with a horizontal drain in and out, you use a wye or a combo.

Cheers, Wayne
great, thank you again.
 

Reach4

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thanks for the idea, that could work but would require taking up a lot of concrete...so I'm likely going to have to tie in to a different drain in another part of the house unless I can tie in between points E and C on your drawing.

Can I put a 3" san T on its back in that location (between E and C)? or would it have to be a Y?

Then keep the vent at 45 degrees until above flood line.
img_4.jpg

A is horizontal wye. F is 45. E is long sweep.
 

PeterT

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What if I install a Y for the vent between points A (the WC) and B and then run the vent to the nearest wall (which is behind the toilet)...this requires reversing the vent direction 180 degrees with some 45's from the Y but I presume that's acceptable as long as I maintain a minimum 45 degree slope on the vent, correct?


as
20220620_152126.jpg
 

Reach4

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The dry vent goes to the lavatory.

How does this new picture relate to the old picture
 

PeterT

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The dry vent goes to the lavatory.

How does this new picture relate to the old picture

See image below. The Y will be installed just after the WC closet bend and a 2" vent will rise from the Y at greater than 45 degrees.

I want to get the 2" vent from the Y into the wall behind the toilet. To do so, the vent would have to reverse direction under the concrete with some 45's ... is that acceptable provided a 45 degree rise is maintained? I would then tie it into the lavy vent above the flood line.

20220620_152126.jpg
 
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