DWV Layout; back to the drawing board?

[beauesq]

Hi all, love this forum! Has been a huge help getting me closer to passing inspection as an owner-contractor updating in IPC country.

Ok, so in this initial layout (image)

A) I tried a rolled wye above centerline for dry venting the toilet and shower only to learn on inspection that dry vent has to run vertical until past the plane of the fixture it's venting, or if 'flat' must be washed by something, so a no go here (see thumbnail inset image).

B) I'd also thought kitchen drain could tie-in last of this dry vented group, but apparently must be after lavs anyway, and since dry vent (A) was a non-starter, back to the well established rule that the kitchen cannot tie into a wet vented soil group.

Also, C) apparently washing machine drain line must be on its own and cannot run with lavs.

And D) my double fixture Tee is apparently wrong and I need a double sanTee (picture)

So we discussed a revised layout: 1) capping dry vent, 2) moving kitchen drain to last, 3) moving washer to own, 4) making washer drain single required roof penetration vent 5) swapping double fixture tee for double sanTee.
Tho it starts looking janky lol

And E) the inspector still wants for some reason to have the shower moved to a 2-3-2 combo wye with the lavs? (not yet drawn in).

Original layout:

revised layout (sans moving shower drain until I understand more):

Thanks for any advice! Passed my rough electrical, surprised to have so issue with the plumbing since it seemed simpler.

 

[Reach4]

Shower should get vented before joining the toilet flow. Run the shower trap arm over to the wall, vent, and then continue to join the toilet flow.

Where is the replacement septic? You might try showing an overhead (plan) view. In your sketch it looks like it might be under the house, and I know that is not the case.

Vent splitting must be at least 6 inches above the height of the standpipe opening.

 

[Sponsor]

 

[wwhitney]

A) Correct
B) The kitchen sink can tie in anywhere that isn't a wet vent. Since the lavs are dry vented, the kitchen sink could tie in upstream of them. But see (E) for why that's a bad idea.
C) The washing machine can join in anywhere (that isn't a wet vent), but it has to be increased to 3" as soon as it joins another drain. So if you don't want to increase it to 3" earlier, keep it separate from the lavs.
D) Completely backwards, the double fixture fittings is fine and is preferred (required?) over a double san-tee. A double combo would be prohibited.
E) The point of moving the shower drain to join the lavs is to let the dry vented lavs wet vent the shower. And then if the lavs/shower join the WC before anything else, the lavs also wet vent the WC.

So the fixture joining order should be lavs - then shower - then WC - then everything else (kitchen sink and washing machine, order doesn't matter).

You'll have 3 vent takeoffs -- lavs, washing machine, and kitchen sink. One of those needs to go through the roof; the other 2 can use AAVs, or join up with the one that goes through the roof.

Cheers, Wayne

 

[beauesq]

Wow, Wayne, such incredible information, blown away! E) I'll go ahead and move shower arm (wet) to join the lavs (tied to washer vent) with a double combo wye + 1/8 bend, C) attach washer drain to 3" elbow with 2" side inlet while extending washer vent thru roof and B) tie in kitchen sink (AAV) somewhere downstream of the wet vents. Now I have the confidence to get back in the crawl space and make the changes, thank you! And, oh man, D) I'll just have to find a way to clarify that a double fixture tee is not a double combo/S trap without hurting anyone's feelings.

 

[wwhitney]

I'll go ahead and move shower arm (wet) to join the lavs (tied to washer vent) with a double combo wye + 1/8 bend

I don't follow this part. Why is it double? The shower + lavs needs to join the WC before you bring in either the washer or the kitchen sink.

I suggest updating your drawing and posting it for confirmation.

Cheers, Wayne

 

[beauesq]

Vent splitting must be at least 6 inches above the height of the standpipe opening.

Did not know this! By luck the standpipe is a few inches below vent split for lavs (tho my drawings didn't capture any height difference.) I believe I have some room to lower box/standpipe, but have had two inspectors not mention it. And thanks for shower venting idea! Here the wall is under a window, but also full of crazy studs, deadwood added to a 70 year old house that makes horizontal-ish boring a pain! Thank you Reach4!

 

[beauesq]

I don't follow this part...
I suggest updating your drawing and posting it for confirmation.

Cheers, Wayne

lol yeah, not sure i did a good clarifying. the lav will cross join the shower on the wc, the washer further downstream at the elbow and last, the kitchen drain where no wet vents remain.

added* the double combo wye i can get from box stores, 3" only so bushings + 2" 1/8

 

[wwhitney]

The double combo you showed is 3 pieces, which would be maybe OK on the horizontal as you can adjust the 45s to get the proper slope (opinions on a horizontal double wye vary). A 1 piece double combo can't be used horizontally, as the two side inlets would be dead level with no slope. But it's better just to use one wye after another. For the layout drawn, the lav/shower wye would have to be upstream of the WC wye.

Also, the side inlet quarter bend is not a drainage fitting. I'd suggest dropping washer drain and connecting it via a san-tee below the quarter bend. That way your lav drain shouldn't have to do that extra little vertical drop after it passes over the washer drain.

Cheers, Wayne

 

[beauesq]

opinions on a horizontal double wye vary ---a 1 piece double combo can't be used horizontally, as the two side inlets would be dead level with no slope.

Also, the side inlet quarter bend is not a drainage fitting.

Wayne

Got it, 1 piece flat double combo makes sense as to why it wouldn't give you your proper drainage slope. 3 pieces sounds like a maybe. And good to know about side inlet quarter bend, was really reaching to make everything fit.

On that note, not much space for a combo after a combo or the vertical drop for washe drain; Next idea 1) taking 3" out to where washer joins lavs and go with double combo combo wye +1/8 (3 piecees) OR 2) re-drawing the line as shown. Thanks for your help again !

idea 1

idea 2

 

[wwhitney]

Your latest drawings don't comply with the requirement that the washer and kitchen join downstream of the bathroom group (lav, shower, WC). That's necessary for horizontal wet venting, where the lav wet vents the shower and WC.

If you tell us what constraints you are facing under the floor, then we could advise you on routing options.

A code compliant variant on the latest idea 2 is below. The double san-tee you have (actually it could be a double quarter bend) isn't great because of difficulty with snaking (so I hear), and I'm not sure that the horizontal wet venting across it is allowed (although it seems to me it should be). In my drawing, red is 2" and blue is 3", and perspective-wise I attempted to draw my lines parallel to the existing lines when possible.

Cheers, Wayne

 

[beauesq]

Your latest drawings don't comply with the requirement that the washer and kitchen join downstream of the bathroom group (lav, shower, WC). That's necessary for horizontal wet venting, where the lav wet vents the shower and WC.

If you tell us what constraints you are facing under the floor, then we could advise you on routing options.

A code compliant variant on the latest idea 2 is below. Wayne


View attachment 77506

Oh man, a puzzle! So between the WC horizontal pipe and the horizontal out the stem wall to septic, I have only 19" on center (A).

With a short sweep elbow veritcal from WC (+lav, +shower), I could just maybe squeeze in the wye to pickup washer drain and still make a long sweep for the septic. The kitchen tie-in wye next would end up with a portion inside the stem wall, but glue-able. I like having a viable option now tho! Also another look at whole thing and you can see how I had ran lav/washer together and now just need to seperate and have wash join downstream of lav at 3" pipe. Enjoy your Saturday, thank you!

 

[wwhitney]

In 3" PVC, a horizontal to vertical street quarter bend uses 4-1/16" of altitude. A vertical to horizontal all hub LT90 uses 4-9/16" of altitude (exclusive of hubs). So together the center to center of the horizontal in/out is 8-5/8". A street 3x3x2 reducing san-tee adds 4-3/4", while a street 3x3x2 wye adds 6-1/2".

You also have the option to replace the LT90 with a street 3" wye and a 3" 45, using the branch inlet on the wye vertical. Then the straight inlet (possibly with bushing) lets you bring in another drain. The street 3" wye in that orientation uses 5" of altitude to the centerline crossing of the two branches, and then another 3-1/8" at 45 degrees off plumb. A 3" 45 is 1-3/4" on each leg, so the 45 degree segment of 3-1/8 + 1-3/4" = 4-7/8" has an altitude change of 70.7% of that, or a little under 3-1/2". That makes the total altitude change of street 3" wye + 3" 45 is 8-1/2". Which is 3-15/16" more than a LT90, but that increment is less that either of the options in the first paragraph.

The upshot is that with 19" c-t-c you have a variety of ways to bring in both the kitchen and the laundry on the vertical segment of the building drain if desired.

Cheers, Wayne

 

[beauesq]

In 3" PVC;

a horizontal to vertical street quarter bend uses 4-1/16" of altitude.

A street 3x3x2 reducing san-tee adds 4-3/4"

straight inlet (possibly with bushing) lets you bring in another drain.

the 45 degree segment of 3-1/8 + 1-3/4" = 4-7/8"

total altitude change of street 3" wye + 3" 45 is 8-1/2". [Which is 3-15/16" more than a LT90 4-9/16" altitude] Wayne

Got it, revised and will see what box store has in stock (street sanT may be an order item) and dry fit to see how I end up! Great information, I owe you tailgate $!

 

[wwhitney]

Connectivity looks good. Possible issues or optimizations:

- You could turn the shower trap outlet 45 degrees (rotate the elbow U-bend joint) and use a wye instead of a combo to connect it to the lav drain.

- If you have the height for the street 3x3x2 wye instead of the street 3x3x2 san-tee, that would be a little nicer arrangement. If you have to order them, you could get one of each.

- A 3" cleanout at the lower horizontal level would be good (required?), so I suggest extending the lower 3" and having a cleanout plug in the end.

- If the kitchen drain is at the same elevation as the washer drain, I think they might interfere in your layout. You could use a 45 instead of a quarter bend and roll the lower LT90 (which would be a 3" combo if you add a lower cleanout) by 45 degrees, assuming the kitchen drain is approaching square to the lower 3" line in plan (as seen from above).

- Or if the kitchen drain is approaching the washer drain square to it, and you can pull the kitchen drain a little closer to the washer, they could join with a combo before the combined drain turns down to join the 3" vertical.

Cheers, Wayne

 

[beauesq]

if the kitchen drain is approaching the washer drain square to it, and you can pull the kitchen drain a little closer to the washer, they could join with a combo before the combined drain turns down to join the 3" vertical.

But..."C) The washing machine can join in anywhere (that isn't a wet vent), but it has to be increased to 3" as soon as it joins another drain."
Wayne

Yes, kitchen drain is approaching the washer drain square to it. And even if more work or less elegant, not having to order any pieces would get me done today

 

[wwhitney]

Correct, I briefly forgot about that 3" requirement. : - )

But the cleanout is an important issue.

Cheers, Wayne

 

[beauesq]

I briefly forgot about that 3" requirement. : - )

But the cleanout is an important issue. Wayne

Oooh, hows this?! I think washer would be considered joining at 3" here. Fun to glue for sure

 

[Reach4]

If you are gluing a joint where getting the angle just right is important, you might consider the Charlotte ConnecTite® Push-Fit DWV Fittings. They cost a premium, but can allow you to rotate, or even take apart. Glue cannot rotate.
Most joints won't need that feature.

 

[wwhitney]

Yes, that's very nice if it all fits. The uppermost 45 could be a 2" elbow with the bushing in part A. In plan the washer has to be parallel to the 3" septic, with the kitchen square to it.

Since combos aren't available street, for A you could use a street 3x3x2 wye with a street 2" 45, if necessary.

One thing I'm not clear on is the pros and cons of moving the cleanout a bit farther towards the washer with a short section of 3" pipe. On the one hand it would move it to a place with more vertical clearance and would reduce the risk of opening the cleanout and having crud fall out. On the other hand there's more horizontal space for crud to possibly accumulate just upstream of the last wye.

Cheers, Wayne

 

[beauesq]

Yes, that's very nice if it all fits. Wayne

D'oh! It didn't fit lol but...found space to fit 3 combos in a row. Length of WC wet vent only about 20", any requirements there? Have parts, hopefully a final check with you guys, and finish in the morning