UPC venting questions

[ben5243]

I planned my bathroom remodel layout with the shower drain to be within 8ft of the "wet wall" where the existing vent and drains are because this is what I read online was the maximum distance allowed (by code and physics).

Now I'm realizing WA state is under UPC code and the trap arm is limited to 5ft so I need a way to vent the shower.

My other limitation is the joist cavity is only 6.5" tall under the shower due to lowered subfloor and drywall for the ceiling below so a 2" trap barely fits

The code seems to indicate you can vent horizontally below flood level of the fixture if there is a "structural condition" and you use waste fittings instead of vent fittings and slope as a drain:

Unless prohibited by structural conditions, the vent must rise vertically 6” above the flood level rim before continuing to horizontal. (UPC 905.3) 
Vent pipe fittings located less than 6” above flood level of rim must be drainage pattern, and pipe must have drainage slope. (UPC 905.3) 
Takeoffs for vents must be above the trap weir, except water closet and similar fixtures. (UPC 905.5) 
Vent pipe inverts are taken off above the center line of horizontal drainage pipe, except horizontal wet vents. (UPC 905.2)​

I've dry fitted what I'm thinking. Can anyone tell me if this is legal under UPC 2015 in WA state? The wye is rolled so that the lowest point on the 1.5" vent connection is above the centerline of the 2" outlet. The 2" from the p-trap is sloped at 1/2" per foot and the vent is sloped 1/4" per foot. The wye is 4ft from the p-trap.

 

[Plumber69]

Maybe you can up size your shower drain to 3inch with a 2 inch ptrap.

 

[Sponsor]

 

[ben5243]

Maybe you can up size your shower drain to 3inch with a 2 inch ptrap.

Trap arm length is determined by trap size, not pipe size and there's no way I could fit a bigger trap. Plus 3in is still limited to 6ft and I'm about 7.5ft from the vent wall

 

[Reach4]

Trap arm length is determined by trap size, not pipe size

I expect you are mistaken. I am not a plumber.

 

[Terry]

Length is determined by pipe size. It takes into consideration the 1/4" per foot slope so that liquid flowing downhill still leaves an air gap above the flow.

If you are venting with a wye there, why not at least bring it closer to the p-trap?

 

[ben5243]

Okay, I misunderstood the table. But the only way to upsize to 3" would be an eccentric adapter because there's no more vertical space above the p-trap (see picture in post #3)
Plus the trap arm length is still limited to 6ft with 3" pipe and I need to go 7.5ft to the stack vent.

The reason I put the wye 4ft from the trap is so it could be "rolled" and then still have enough vertical space to slope the 1.5" vent at 1/4" per foot.

I could move it closer but I would have to slope the 2" drain steeper than 1/2" per foot. Is that allowed?

Or am I misunderstanding UPC 905.2 and the wye can lay flat?

Thanks

 

[ben5243]

Also, just to clarify what I'm asking - the vent connecting to the "rolled up" wye is a dry vent because there are no fixtures upstream. Unless I'm misreading the code (totally possible, I'm very new to this) the sections UPC 905.2 - 905.3 don't seem to specifically exclude dry vents.

The same concept is used for island sink venting, I just don't know if an inspector will approve this or not and I don't want to continue if I put my shower in an impossible-to-plumb location.

 

[Cool Blue Harley]

Glue it up, your installation fine.

I prefer a 1/4 inch per foot. I don't like excessive grade.

You are correct. The invert of the vent (bottom of pipe), is required to be above the centerline of the drain. Yours is perfect.

A agree with Terry, you probably could have rolled your vent off closer to the trap, but don't sweat it.

Remember, the vent 90 not shown in your photos, going from horizontal to vertical under the wall, is considered a drainage fitting and must be a medium sweep.

 

[Terry]

It may not pass. I used to plumb them that way in my olden days.
An Island vent can drain down, and has a cleanout to clear the line if needed. I would check with the local inspector and ask.
Granted that also drains down, but the odds of the water getting higher than the top of an Island loop is pretty small.
Lately I have tried much harder to lay out the plumbing so that I can run a vertical vent. Every so often they tweak things here in Wet Land.

 

[ben5243]

I will try to contact an inspector. The last time I called the planning office with a code question they only let me talk with someone in planning who was very helpful, but not the person with the final say (inspector). I'm just trying to get as much information as possible before asking questions that make it sound like I'm clueless.
I'm in Snohomish unincorporated if that helps. I didn't realize you were in Bothell - do you do remodel work? Every plumber I tried calling told me they don't do remodels so I'm going to see how far I can get myself.

For the 90 going up into the wall - a 90-degree "elbow" is medium sweep, right? Anything not called a "vent" fitting or "long sweep" is medium?
I purchased this one:
https://www.lowes.com/pd/NIBCO-1-1-2-in-dia-90-Degree-ABS-Elbow-Fitting/3438914

 

[Cool Blue Harley]

Island venting is unique. Other than floor mounted fixtures and island fixtures, no other fixture is permitted to have it's vent installed below the floor.

In a perfect world, all venting would rise vertically, defined as " continuous vent". But sometimes there are obstructions in the building that prevent this ideal condition.

If you install a floor drain where the distance from a wall exceeds the trap arm distance, the vent would have to be placed in a horizontal position until it could turn vertically in a wall.

That installation is 100% UPC code compliant.

The 90 you need is actually called a long turn.

 

[Cool Blue Harley]

No. That is not it. Glue a street 45 into a 45 and you can't go wrong. Or duplicate that bend.

 

[Cool Blue Harley]

Maybe you can up size your shower drain to 3inch with a 2 inch ptrap.

A trap for any given fixture can never be more than one pipe size larger than listed in the drainage fixture table. 2&1/2 inch is considered a pipe size. You can never have a three inch drain on a shower.

The trap, by code, must always be the same size as the trap arm. At least in the UPC.

 

[ben5243]

Thanks!
I'll get a long sweep 90 for that. I had confused medium being allowed in a horizontal to vertical connection (which is how my brain thinks about the vent), but this would be considered a vertical to horizontal connection because the direction of "flow" is down so a long sweep is needed.

 

[ben5243]

Circling back to this, I've drawn up the rest of the plumbing for the bathroom and what I think will pass inspection. Hoping someone familiar with UPC code could give it a once over. A plumber I talked to recommended using two 22 degree elbows right out of the p-trap to get the height needed to roll up the wye (unlike what I posted in my previous pictures).

1.) There is a 3" cleanout before the shower and toilet drain enters the existing stack for a test plug. Should I add test plugs to the 1.5" tub drain before it enters the stack and the lav drain before it enters the stack? I'm told I'll need to plug these and fill the vents up to the roof with water before inspection.

2.) Is the branch vent on the lavatory necessary or redundant? There's nothing that drains into the stack above the lav drain but there are other branch vent tie-ins.

3.) Anything else that looks illegal?

Thanks!

 

[Cool Blue Harley]

All wrong.
Hire a plumber.
Not the one you talked to.

 

[ben5243]

What's wrong that goes against UPC code?
The 22 offsets off the p trap only drop the 2" drain 1.5" before venting. That's the only way to get some height in the joist cavity to roll up the wye and give the vent proper slope. The way I had it before had excessive slope before the vent

 

[Cool Blue Harley]

I was not referring to the p- trap offsets.
They are the least of your problems.

 

[ben5243]

Decided to continue seeking help and figure out why my proposed layout is wrong. Correct me if I'm wrong, but I think the shower drain can't tie into the vertical section of the w.c. drain. I can't find any language in the code that prohibits this, but it seems to go against the "intent" of the horizontal wet venting code. The toilet would need to be vented upstream of where the shower ties in.

It seems that the tub drain also cannot connect to the stack as it would create a vertical wet vent above the toilet cross. Vertical wet vents can only accept trap arms per UPC 908.1 and because the tub is vented, it's a horizontal branch and not a "trap arm". I don't understand the logic for this code, but it is written that way.

The vent on the lav arm also makes it not a trap arm, but because the trap arm is only about 32", I don't need the vent and the lav can stay.

Attached is version 2.0. I drew up the rest of the DWV for the house to better see the "big picture". I made a few assumptions as to what's going on inside the downstairs wall but I know where each pipe comes out of the slab based off some old pictures I took when the bottom of the wall was open. So it should be close.

The shower drain would alternatively go "around" the w.c. drain and into a double-fixture fitting that serves the bathtub on the other side of the wall. It's a bit more work this way as I'll have to cut out and lower the fitting under the wall inside the floor because it's too high right now and rework the bathtub trap.
The only way I can figure out how to properly tie in the tub drain is to cross 2 sistered 2x8 joists and be wet vented by the shower vent. I can do this almost at dead-center on the joists and a 2" hole is less than h/3 of the joist, plus they are doubled up already. I'd still rather not drill the joists if you had a better idea how to tie in the tub?

Thanks again

 

[ben5243]

Well I just thought I'd swing back here and update. The drawings in my last post have one minor error - the bath and shower branch drain need to connect below the trap arm for the adjacent tub/shower. Only trap arms can connect to double fixture fittings. I sent my drawings to the building inspector and he let me know that portion was incorrect. I ended up pulling out the double fixture fitting and putting in a new drain assembly, trap and connection to the 2" stack while I was in there (instead of just capping off the other inlet like this drawing).

Passed rough-in inspection today.