Please help with Small bathroom DWV in floor on slab ... no wall space

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Jrol22

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Hi and thank you for any knowledge/insight. I have done mostly repair plumbing and now I am having difficulty wrapping my head around my DWV system for a new bathroom in a very old, very small house. Most of my reading shows layouts with soil stacks in the wall etc. I don't have such a system.
The constraints are as follows:
Single story house, 3" drain pipe (to septic).
The bathroom (only bathroom) is being built onto a slab. I am using rough-sawn 2x8 framing, so that is the height I have to work in.
The house is built (in 1860) like a barn, post and beam, with no walls to put anything in. Everything is in the floor or exposed. I may just leave the supply exposed.
The bathroom is small (<6X8) with a need to have the drain for the washer tie in from the "far end" and go through the bathroom.
The order of fixtures from farthest to nearest is washer from other side of bathroom, sink, tub, toilet connect to existing 3" drain.
There is no vent in the line at this point (the part of the house with a vent is being demolished). NY state permits AAV's but only if there is at least one true vent
I am having a lot of trouble placing (fitting) a vent and and figuring a sensible layout. With no wall space I am hoping I can share a single vent pipe among all of these fixtures with no above floor connections.
I also am not clear if one can use a combo (tee/wye) directly under a toilet - in my limited experience I have only seen a closet bend with nothing directly upstream of the toilet.
According to my reading the washer itself would require a 2" drain, I therefore figure the pipe serving the washer, sink and tub should be 3" before tying in with the line at the toilet. Seems a bit much..?
Can this then tie into the drain under the toilet using the previously mentioned combo? or do I need the toilet to closet bend into the combo laying flat.

Also, if I tee off a vent somewhere in the middle can it serve all of these? that is to say: I tee the vent off upstream of the toilet within 5ft of the washer - Is that proper venting, and is 2" enough?

One more, If I kept the gray water fixtures separate from the toilet, could I (and how so) share the vent? I suspect the connection would need to be upwards of 42" above the drain line? Or is that just not done for gray water.

Oh I doubt I made myself clear, but I hope someone finds it worthwhile to clarify.
thank you
John
 

Tom Sawyer

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As detailed as you post is, it's still pretty hard to give you definitive advice without a drawing or photo. I can tell you that sanitary tee's can not be used in the horizontal position for waste. Depending on it's orientation under the toilet, it may or may not be acceptable. Keeping the gray water fixtures separate opens a whole new can of worms and is generally not feasable in most residential applications.
 

hj

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quote; With no wall space I am hoping I can share a single vent pipe among all of these fixtures with no above floor connections

That is NOT going to happen, unless ALL your traps are under the floor, which would create a different code violation. Your situation is much too complicated for us to try to give you a solution. ONLY a plumber on site can work it out, but then that is why we go to school for 5 years and study books. You are trying to learn it in a few minutes with an Email.
 

Jrol22

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Well, you guys go to school so you can efficiently know what to do in most any circumstance - such that you can earn a living doing so. If you were to futs and fuddle as much as I am on one bathroom you'd starve to death! I know I cannot learn plumbing in one inquiry, but I should be able to learn to plumb one bathroom in a week or so with enough wasted energy and a background in the trades.
I understand that I cannot run all of the fixtures to this one vent under the floor, I realize I would likely have sewage filled vents - But if I give the system a 2" vent between the tub (ptrap exposed) and toilet can I use AAV's for the washer and bathroom sink?
Here is a poor drawing (MS paint)
I bathroom.JPG
I will forget the gray-water thing so it is less problematic. And I can just run the toilet with a closet bend to a wye with so my question is more or less about the venting and its sizing - does this look reasonable?
I would also think the line from the washer and sink to the tub could be 2" not three...?
Thank you for any response,
 

Jimbo

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You should not vent a washer with an AAV. I can't say if the code specifically prohibits etc.
 

Tom Sawyer

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The only caviet I see here is that I would be running 3" right under the lav and make sure the laundry dropped into it. An AAV is as Jimbo pointed out, pretty much up to what your local inspector says but remember that an AAV lets air into the plumbing system and not out and your washer is a pressure flushing fixture which pushes air out of the vent system so quite often a smart inspector is going to nix an AAV there. Ther other issue will be your trap to vent distance which will apply to the tub. Use of the 3" to the lav should keep your distances within code.
 

Geniescience

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New vent near the washer and lav sink. Make the tub drain go pick up the vented line within critical distances. For the tub drain, you could use 2" pipe for the tub P trap and drain to increase self-venting and give yourself more distance to run before it hits critical distance. ((the Slope of this tub drain must be only 1/4" slope down per running foot, not more!)). Do not bring the new vent to the Toilet. You can split the vent into two 2" vents for the washer and lav, even tho they are very close.

Combine the Toilet drain as the last link in the chain, after all the other things have been vented / combined / configured together. Repeat: Toilet downstream. Not upstream of your other drains.

The above is how i would dream it to be without an AAV, but this is not what I would have built ultimately, because I would consult more.

Some will say the washer should be combined separately, downstream of the toilet. That too is good. You can split the vent into two 2" vents for this purpose.

This is about all you will get over the internet. There is a lot of 3D thinking involved in plumbing, and every connection point requires a specific shape of Wye or Tee, so Do Not Think You have learned anything that you can act upon with certainty. Hiring a Master Plumber is worth it for you in this case.

hope this helps.

p.s. I may have mis-read your original post. It is hard to read.
 

Plumber2011

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Hi John,

I'm thinking you could just WET VENT the toilet using the tub drain and that 2" vent through the roof.

You would set the 3"x2"wye for the tub and 2" vent through the roof so that it rolled above the center line of the toilet drain...what makes it a vent in this case (see image below).

The washer and sink should be fine on a 2" drain line (but do check local requirements). The sink can have an AAV, but that washer should really have a minimum 1.5" vent going up and through the roof (increase to 2" just before penetrating the roof). Perhaps this pipe could be painted to match the wood???

In my opinion, full size 2" Cleanouts should be installed under the sink, at the washer drain, and at that 2" vent by the toilet, if possible, for best job!

That's my thoughts...Good luck!

PS: Please check local codes to confirm that wet venting is allowed, OK?
 

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Tom Sawyer

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Hi John,

I'm thinking you could just WET VENT the toilet using the tub drain and that 2" vent through the roof.

You would set the 3"x2"wye for the tub and 2" vent through the roof so that it rolled above the center line of the toilet drain...what makes it a vent in this case (see image below).

The washer and sink should be fine on a 2" drain line (but do check local requirements). The sink can have an AAV, but that washer should really have a minimum 1.5" vent going up and through the roof (increase to 2" just before penetrating the roof). Perhaps this pipe could be painted to match the wood???

In my opinion, full size 2" Cleanouts should be installed under the sink, at the washer drain, and at that 2" vent by the toilet, if possible, for best job!

That's my thoughts...Good luck!

PS: Please check local codes to confirm that wet venting is allowed, OK?

I don't think that even if he rolls the wye at 45 that he can get the tub drain in there and not have a section of flat vent there. You are in Mass where they sometimes allow flat venting but most codes won't. All parts of that section need to be rising until they get 6" above the lav vent. And.... I doubt the AAV on the washer will fly either or at least is shouldn't, after all what good would it be since it allows air in and the washer pushes air out?
 

Jrol22

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You guys are great, I thought the thread was not going anywhere. I am willing to change anything, there is no vent yet there. I am trying to wrap my head around the wet vent scenario.
I placed the vent there in the diagram to use for both tub and toilet, thinking my toilet vent could "climb" that far under the floor.
The whole house, by my calculations will only have 9 dfu's so I thought a two inch vent to the roof (increased to three at the roof for frost closure) would be enough. I have come to grips with the idea that if an AAV won't work I may have to run the vent from the washer and lav at 42" above the floor.

I think I follow your wet vent but the heights seem to get awry with the tub p-trap.
I am having trouble finding a spec on the tub trap height with respect to the main drain line - I envision it getting a charge of bad water in the trap if toilet flushed while washer draining - that is if I fit the trap under the floor. (the tub is freestanding with no definite height) Could you advise on this dimension?

Part of the reason for the toilet going where it is was to bring the drain pipe close to the slab for the most room to work on the rest of the bathroom. I am getting stuck with heights though, a 3x3x2 wye laying at 45 with a 45 street pretty much eats all of my height. I sure like the separate wash lave 2" pipe though!

As for the AAV
But I am not too sure what you mean about "pushing air out" would not the main vent, at the toilet for example, relieve that pressure?
Here is what I find in the NY code:

"P3114.3 Where permitted. Individual vents, branch vents, circuit vents and stack vents shall be permitted to terminate with a connection to an air admittance valve."
"P3114.7 Vent required. Within each plumbing system, a minimum of one stack vent or a vent stack shall extend outdoors to the open air."

I don't see why they would not allow it, but the Idea of a device replacing something as reliable as a pipe does bother me.

Thank you all again - I am very grateful, I need to put this bathroom together so that I can demo part of the house and close it all up before the cold comes (the only bathroom is in the to-be-demolished part of the house)
 

Tom Sawyer

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Take a good look at this picture and note how the wet leg section of the lav drain, from it's trap to tthe wye that serves the WC becomes the vent for the tub, the shower and both lavs. This works on the principal that the horizontal drain, if properly sized (2" or larger) will never be full of water and therefore air is able to move above the water line. IPC will allow 2 bathroom groups ( toilet, lav, sub/shower ) to be wet vented with a single 1-1/2" vent. Which in the illustration would be the pipe that comes off the top of the double sanitary tee that recieves the discharge from the lavs. You can only wet vent bath groups. Not kitchen sinks, mop sinks or washer connections so you will have to individually vent the washer. Again, an AAV on a washer is a waste of time because it does not allow air to escape ( for obvious stink reasons )

Horizontal-Wet-Venting.gif
 
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Plumber2011

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Tom said, "And.... I doubt the AAV on the washer will fly either or at least is shouldn't, after all what good would it be since it allows air in and the washer pushes air out?". Tom, I never said to put the washing machine on an AAV. If you actually read my post I said, "but that washer should really have a minimum 1.5" vent going up and through the roof (increase to 2" just before penetrating the roof). Perhaps this pipe could be painted to match the wood?" Just so you are clear on that, OK?

And we aren't talking about flat venting...talking about WET VENTING!!
 
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Jrol22

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Thats a nice diagram! Thank you. Is this accurate "IRC does not require vents for toilet"
I just found the statement in NY code "The developed length of the fixture drain from the trap weir to the vent fitting for self-siphoning fixtures, such as water closets, shall not be limited."
If this is the case I am in a whole lot better shape: Please confirm or deny the following
To relate the set-up to your diagram - Could I not just basicaly put the tub where the shower is in your diagram (telete the BT and one lave from the diagram as well)
Use a 2" vent stack for the lav
bring the washer vent into the 2" stack at 42"+ height
BUT bring the washer drain (2") to the line downstream of the WC
Am I missing something, becauest that seems too good to be true?

also, I know its funny business, but it seems to me that if the tub p trap is just upstream of the WC - you could get a spill over of WC into the trap from a fluch...no?

You may have saved my rear, Thank you!
John
 

Jrol22

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plumber2011
Thank you for the reply, I think he was referring to my last post about AAV's - Neither you or anybody else suggested an AAV should go there. Could you chime in on the diagram and my adaptation - it seems that I was over thinking. BTW I cannot find our code as it pertains to the flat wye.
Thank you again,
John
 

hj

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quote; I understand that I cannot run all of the fixtures to this one vent under the floor,

I will address this one statement before I try to slog through the other answers. You not only cannot run ALL the fixtures to a vent under the floor, unless it is done properly you cannot run ANY fixtures to it, and then it would be limited to ONE fixture.
 

Tom Sawyer

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Thats a nice diagram! Thank you. Is this accurate "IRC does not require vents for toilet"
I just found the statement in NY code "The developed length of the fixture drain from the trap weir to the vent fitting for self-siphoning fixtures, such as water closets, shall not be limited."
If this is the case I am in a whole lot better shape: Please confirm or deny the following
To relate the set-up to your diagram - Could I not just basicaly put the tub where the shower is in your diagram (telete the BT and one lave from the diagram as well)
Use a 2" vent stack for the lav
bring the washer vent into the 2" stack at 42"+ height
BUT bring the washer drain (2") to the line downstream of the WC
Am I missing something, becauest that seems too good to be true?

also, I know its funny business, but it seems to me that if the tub p trap is just upstream of the WC - you could get a spill over of WC into the trap from a fluch...no?

You may have saved my rear, Thank you!
John

IRC and IPC both have the same verbage as regards venting a toilet in that the distance from fixture is "unlimited" which pretty much means that as long as there is a vent in the house somewhere you are good to go and..... it makes sense because. Toilets are full siphoning fixtures. Every time you flush, the trap empties and is re-filled by the flush valve. They are designed that way so that the trap is self scouring.

My apolgies to plumber 2011, I mis-read your post as regards the AAV use on the washer. NY may well allow flat venting, quite a few localaties do unfortunately. See my flat vent thread for reasons why I think it's a bad idea.
 

Jrol22

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Thanks again for all of your help, please take a look and let me know if I am doing ok, I realize (Hj) that I started far from it. I don't think straight all the time when it comes to venting.
bathroom wet vent.jpg
The washer shares only the dry portion of the wet vent going to the roof - but its drain meets up with the system after the wet vent.
 

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Tom Sawyer

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As long as the distance from the tub to the lav is proper you are good to go
 
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