2 bathrooms new add-on construction-single floor to 4"ABS main

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Road Glide

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Lurking here and time to register and throw out a plan for input. Will be add-on new construction, 2x6 exterior & interior walls. UPC code area and the home has an existing 4" ABS main 10 away in crawl space.

1) Question where to locate vents? Would like to vent 2"out of the two lavatories or one 3" somewhere between WC and showers.
Luckily every fixture would be in close proximity nothing over 8'.

I understand washer/dryer is not in bathroom group but can drained lastly downstream. It would be located next to Lavatory in 2nd bath on laundry room wall. Could share it's own vent with 2nd bath lav over the flood plain 2" vent.

Toilets (WC) would be first to drain, with then lavs, then showers, then last, washer downstream.
All drains would be 4" (WC), then 2" in 4" for showers, lavs and washer...all ABS

Any thoughts would be appreciated before we begin.
 

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wwhitney

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1) You will need a dry vent take off for each lav and for the washer. The lav vent takeoffs have to be 2" to wet vent the WCs. The washer vent takeoffs can be 1-1/2". Anywhere at least 6" above the flood rims the vents can combine (e.g. in the ceiling or attic), perhaps to a single 3" roof penetration.

2) There's no upside to running any new 4". Just use 3" for the WCs and branch drains, and 4x4x3 wyes to connect to the existing building drain.

3) On the wet venting, starting at the lavatory and going downstream, the order must be: lav trap - lav vent takeoff within the distance limit - wye where the wet vented shower comes in - wye where the wet vented WC comes in - any other dry vented drains (e.g. the washer). You can't have the WC come in upstream of the shower if you want to wet vent the shower (but you could instead dry vent the shower).

Also, with wet venting, the trap arm is considered to end at the wye where the fixture drain joins the vented lav drain. So your WC flange to wye distance is limited to 6', and your 2" shower trap to wye distance is limited to 5' of run and 2" of fall.

Cheers, Wayne
 

Road Glide

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This my horrible drawing of the proposed system.
1) Can the lav in the 2nd bath and washer vent be combined if vent is 2" or 3", above flood rims (at least 6") and still enable the showers and WC to be wet vented?
2) Showers and lavs joining the main upstream, do the wyes need to be horizontal or 45 degrees?

As far as the 2 WC's, I could employ a 4 in. x 4 in. x 3 in. x 3 in. ABS DWV 45-Degree All Hub Double Wye and bring the outlet downstream to the main. Or just bring 2 different 3" lines with wyes as shown.
The washer drain would still be after the WC's as pictured.
Trying to keep this brief...
 

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wwhitney

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1) The washer dry vent only needs to be 1-1/2". The washer dry vent and 2" lav dry vent can combine as a 2" vent, that has no effect on wet venting.
2) The shower/lav wye that joins the drains and wet vents the shower should be horizontal, as the total drop of the 2" shower trap arm is limited to 2". The drop is measured to the "crotch" of the wye where the drains actually join.

Also, the UPC only allows wet venting one bathroom at a time. So the lav/shower from one bathroom needs to be kept separate from the lav/shower of the other bathroom. Then each lav/shower picks up one WC to wet vent, and only then can the bathroom drains combine.

Double wyes shouldn't be used horizontally, as they are flat. Individual wyes let you set the pitch of the branch inlet properly and independently.

Cheers Wayne
 

Road Glide

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Redrawn....is this better? Actually WC would be set closer to exterior wall but drain as shown. UPC only allows one group to wet vent then join main.
 

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Road Glide

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Saw this on forum.....I don't know if this would work because of the one wet venting rule with UPC...but curious.
Please disregard this layout...something I saw that was similar but not workable
 

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wwhitney

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Edit: this response is to post #6

The connectivity is good. The drains can all be 2" except the WC and downstream of it needs to be 3". Bear in mind the limits on the shower trap arm length and the WC fixture drain length mentioned in the last sentence of post #2.

Cheers, Wayne
 
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John Gayewski

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The connectivity is good. The drains can all be 2" except the WC and downstream of it needs to be 3". Bear in mind the limits on the shower trap arm length and the WC fixture drain length mentioned in the last sentence of post #2.

Cheers, Wayne
The shower vertical wet vent needs to be 3"as drawn. I'm not sure your saying differently but since you said the drains can be 2"it's a bit confusing since the combined shower drain/vent is actually 3".

Are you saying vent through the lavs and change them to 2".
 

wwhitney

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The shower vertical wet vent needs to be 3"as drawn
I was responding to post #6, thanks for clarifying. Apparently post #7 snuck in as I was formulating my response.

As to post #7, that's a no go for the UPC. A variation on it would work with both showers over one WC and vertically wet venting that WC (which would require a 3" vertical wet vent, as John comments), and the other WC wet vented horizontally by the two lavs, and then the two sides join last.

Cheers, Wayne
 

Jeff H Young

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A lot of planning going in to this sounds like a good plan , consider your clean outs if getting an inspection.
 
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Road Glide

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Considering plumbing DWV 2nd bath first down to 4" main where WC meets with wye and then 4x4x2 wye for washer drain (last outlet to main trunk line). Can't do this all in one day, so need to protect the system from critters or debris.
Leaving or installing the other 4x4x4 wye for main bath with closed stub till I can get to it. NO testing or use till all is done.

Jeff H..... not really a "do-over" guy....one and done is best...
Subscribe to JLC but they refer to the IPC which doesn't work for me but is good reading...especially wye placement, ptraps, etc.

So, without looking at my revised diagram in Post #6.....it would be 2nd bath lav with 2" vent to wet vent the shower, WC, washer drain.
Then 2" shower, then WC to main followed by 4x4x2 wye for washer drain. If I can I would like to combine lav and washer drain but then washer would be upstream.
Luckily, everything is close within 4-8 ft so parts (ABS) won't be a killer.

I noticed the shower drain in a kit was PVC as well as the washing machine wall drain. Concerned about joining ABS & PVC especially behind the washer wall. Use the green glue or run PVC down below flow level and then join ABS.
Clean out side 15-20 ft already, but I plan to install clean outs on both runs up stream...have 3 ft crawlspace...dirt :( with some rock ..
 
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