3 fixture bathroom sanitary vent layout

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Reelbusy

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Good morning, so trying to wrap my head around wet venting vs dry and this simple 3 fixture bathroom with slab.

Everything cast under the slab is gone at one point when house was moved off septic pvc was ran all outside has a newer line running under slab to this bath wall.

So layout is simple, main drain line comes from under wall right there is shower there drain can be to right or left i have it right in drawing, to left toilet and then lav. Can i do something like this? i have to check distances but figure 32" deep shower + 15 toilet offset too one side, it's little tight making the shower bend but seems doable if not i can run the toilet line under the wall too so it's further down. If i understand from reading with a wet vent this toilet should be the first unit downstream so when flushed it's not passing minor fixtures (otherwise in this drawing the shower would need a vent too if the shower was first to connect going out the wall?)

so order of connection here from wall wye -> toilet, then immediately after wye-> shower, then on to a sweep or something to go over to the lav+ vent. Just wondering if this is simplest way to keep concrete cutting to a minimum and if that wet venting is correct (using appropriate pipe sizes i understand)

thanks for any help.
 

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Tuttles Revenge

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Looks like Florida uses International Plumbing Code. They allow 2 bathrooms combined in a horizontal wet vent.

Your drawing works for IPC and also if you happen to be UPC it works too.

912.1Horizontal wet vent permitted.​

Any combination of fixtures within two bathroom groups located on the same floor level is permitted to be vented by a horizontal wet vent. The wet vent shall be considered the vent for the fixtures and shall extend from the connection of the dry vent along the direction of the flow in the drain pipe to the most downstream fixture drain connection to the horizontal branch drain. Each wet-vented fixture drain shall connect independently to the horizontal wet vent. Only the fixtures within the bathroom groups shall connect to the wet-vented horizontal branch drain. Any additional fixtures shall discharge downstream of the horizontal wet ven
 

Reelbusy

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thank you for the reply and that ipc and upc information,

i realize there's some maximum distances to fixtures in my sketch is there anything wrong with those two wyes for toilet and shower being one after the other? there's going to be about 16" of play there between wall and centerline of the shower to tie both in (so that the toilet is first so it doesn't run past the shower).

Worst case i figure i can tie the toilet in further down on other side of wall.

just looks funny when i visualize and sketch it, when i cut the slab up i may have a bit more horizontal play with that shower line. That new line outside the wall isn't deep when they tied this bath in, i may have 6+ inches or so maybe inside to make sure everything sloped ok so may end up digging outside anyways, i'll know more once i cut.

If i tied the toilet in between shower and lav i guess would need an additional vent at the shower prevent any potential siphoning from the toilet running past that line? in that scenario i guess that lav is wet vent to the toilet and shower is dry vented.

This drawing seems simpler though, just gotta tie it in ok in that 16" or so of space.
 

Tuttles Revenge

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I don't think there is any concern of the distance between the shower and toilet fittings. The individual trap arms from that 3" do need to be maintained. I don't know IPC from memory, but the trap arms are pretty long. The 3" should be continued up to the sink tho to maintain an end of line cleanout. Unless IPC allows the toilet itself to be that CO.

And I don't see in the IPC that the toilet must be the last fixture in the group. That is the way the UPC has HWV'ng but in my area we can place the toilet in any part of the series of fixtures. So I think you can place the toilet between the sink and the shower.
 

Reelbusy

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thank you for the advice. Yeah i've read various conversations on that toilet position in this forum in the past several ways depending on which code. Found some older posts from terry basically saying the low flow moves water faster less volume thus he prefers it past the minor fixtures to prevent ptrap siphoning, but as you point out seems debatable depending on the code and others experience. But yeah same here if order doesn't matter in this sketch and existing drain pipe location it's much easier to put it between shower and lav than try to squeeze it at the end (which i'd have to double check those trap arm lengths)

I'll do a bit of measuring to get a better idea how things work out and double check those distances.

I was planning on having that cleanout under the sink too thanks.
 

Jeff H Young

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I don't think there is any concern of the distance between the shower and toilet fittings. The individual trap arms from that 3" do need to be maintained. I don't know IPC from memory, but the trap arms are pretty long. The 3" should be continued up to the sink tho to maintain an end of line cleanout. Unless IPC allows the toilet itself to be that CO.

And I don't see in the IPC that the toilet must be the last fixture in the group. That is the way the UPC has HWV'ng but in my area we can place the toilet in any part of the series of fixtures. So I think you can place the toilet between the sink and the shower.
Tuittles do you know if your code allows w/c not be last or if its just general practice and allowed? TIA
 

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Tuittles do you know if your code allows w/c not be last or if its just general practice and allowed? TIA
Washington state amendments allow the WC to be anywhere below the dry vented fixture. Its the only fixture that can't be above. Its not required to be the last in the line.

The UPC is different from IPC in that only 1 bathroom group per HWV system and toilets must be the most downstream fixture. (Theoretically because they want the other fixtures to "wash" the drain after the toilet has been flushed to increase the water flowing after the toilet flush has dropped its turds 30ft down the drain.)
 

Reelbusy

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ahh ok so that would make sense, post wash down (related to low flo maybes) so maybe the siphoning thing i remember reading is more of a personal opinion thing....probably can screw it up too with too much slope and depending on volume

found it i was reading opinion here other day: https://terrylove.com/forums/index.php?threads/does-this-wet-vent-meet-code.43885/#post-315590

but yeah conclusion about the same. Well heck having that toilet between the 2 certainly will be much simpler given the space limitation to tie in at the beginning. thanks!
 

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Interesting. I've been installing horizontal wet venting since the day they allowed it in our jurisdiction. And since our state amended the rule about toilet placement in between other fixtures in the group, I've never seen one siphon a trap. Everything we do is horizontal wet vented and I've installed some funky layouts to make it work. I've even set up a HWV system in our parking lot to see if I could install it wrong and see what would get it to fail and couldn't.

Tho I think it might be good to try again with toilets in the middle of the system since my tests were done prior. Wish I could get my hands on some clear pipe!
 

Reelbusy

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yeah i may have read too much into that and a few others saying similar and thought ok this is why last in system, but your reasoning makes most sense to me (given a low flo world). Given age of that thread the siphoning aspect (which think i've read other threads terry mentioned seeing that siphoning too ...wish i had bookmarked those for curiosity) it apparently isn't a common thing, and i would certainly think though i'm not a plumber think slope, trap and pipe lengths , come into play if so just pondering fluid/air dynamics of it.
 

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Could even run the toilet straight over to Next to the wet vent, then run parralel until its max trap arm distance before tieing into the wet vent. Might allow for max settling of the water before it passes by any other fixtures. Not sure it would really be a benefit, but I don't see it hindering.

1685133031148.png
 

Reelbusy

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Yeah that's a good idea. When i get this fitted up i think i'll just do a straight run, and i'll test for grins, funnel and bucket of water down the flange, stick a diy scope cam i used to figure out the shape of thing, put it down in the shower ptrap or measure the water someway...just out of curiosity.
 

Reelbusy

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not really an issue i had just ran across threads where terry and few others mentioned possibility of ptrap siphoning from a toilet flushing past a shower in a wet vent , doesn't seem to be an common issue. tuttles helped clear it up pretty well.
 

Reelbusy

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Good to know as it made that saw cut go much quicker!

Wonder if can get some related advice, i've been pondering this but wondering what pro's would do. History is this house got new pvc drain lines ran to the footer ages ago (florida slab) but everything else under slab is shot. The above is because i had a pvc drain outside of that wall.

I have a middle bath that is an exact same layout but getting it to the 4" sanitary pvc is bit more challenging. I've saw cut to where i can tie in. It's about a foot down. the layout is simply this a 4" line was ran all around the back of the house and to the other side back in the day leading to tie into at the slab to old cast iron with couple wyes. Eventually that tie in area was enclosed , concreted over and freaking ton of leveler apparently lol. Figured all this mess out with a diy sewer cam lol

So it's like this:

4" pvc ----> wall ---5 foot --> tie to old cast under enclosed part slab (also burying a cleanout).

I've saw cut from a middle bath where i can tie into the above.

If you comprehend this so far i'm wondering which is easier in the trench...

if after cutting off the old wyes (i don't need those runs anymore) if i should make space to pop a 4" or 4->3" coupler on. Or simply since i've got to cut the pipe outside the wall to add a cleanout there run a 3" thru the 5 foot of 4" under that slab in the pic (so that section becomes a sleeve) and then it's simply another 4 -6 feet of 3" to service the bathroom.

So in this picture i'm standing in the bath looking at where i'll be tieing in. On the far side of pic that wall is where i'll put the outside cleanout. Seems since this is just serving a single bathroom i could just cut the 4" take out the old wyes,etc and cut outside drop run the 3" thru the remaining 4 under the slab without having to finagle a 4 or 4-3 inch coupler 12" down, get it clean,etc and then put my cleanout on out there.

I guess the ? becomes is about a 14' long run of 3" ok since it's serving just a single bathroom to tie into the 4" outside the wall. Or finagle a coupler on in that trench and transition there to 3 or further up.
 

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