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Thread: Changing direction of new PVC pipe while replacing slab on grade in new house

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    DIY in AZ emd36's Avatar
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    Question Changing direction of new PVC pipe while replacing slab on grade in new house

    Hi,
    I'm thinking of changing the direction of the drain pipes in the master bath area of our house remodel.
    We had to replace the slab on grade in this house because it was severely cracked due to expanding soils.
    We are replacing all the old cast iron with PVC. The lower portion of the drains were severely corroded and cracked.
    Here is the proposed change of direction in order to get the toilet vented without any fixture in between the toilet and the vent. (IPC)
    Name:  Sewer Change of Direction_4.jpg
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    The vanity is between the toilet and the shower on the other side of the vent which will be incorporated into the shower wall. Here is one proposed method of connecting the vanity (into the vent?)
    Name:  Existing sewer_4.jpg
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    I think we need to run another 2" line from the vanity to the main drain to avoid wet venting the toilet vent. I can still bring the vent up from the rear of the vanity to the main 2" vent but run the drain at a diagonal across to the main drain.
    The tub will be across from the toilet and the vanity, and we could combine the vanity drain and the tub drain on one 45 degree v connection to the main drain and then vent the tub up to the ceiling and over to the main vent.
    Name:  Existing sewer_6.jpg
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    Any issues with this plan? Thanks...

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    Moderator & Master Plumber hj's Avatar
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    It it all too confusing to try to make any sense of any of the drawings. Give us a "floor plan" of the fixtures then it may make sense. In fact, maybe NONE of your plans is the best one.
    Licensed residential and commercial plumber

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    DIY in AZ emd36's Avatar
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    Sorry the photos are confusing. They show the old pipe layouts so that the differences are noted.
    Here is the floorplan with the size pipes and layouts for the whole house. The only plumbing not being redone is the bathroom in the back between the two bedrooms, that was ABS and is connected to the new PVC with a fermco fitting where it was connected to the cast iron.
    Name:  Dibble Res_FP_Plumbing_1.png
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    I'm most concerned about the master bathroom. The new layout has the toilet drain vented to the old vent and the shower comes in on the other side of the wall that will hold the vent piping. The lavatory in between is draining to a 2" pipe that joins to the bathtub drain and on to the main drain in green.

    Thanks....

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    DIY in AZ emd36's Avatar
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    Well, I borrowed some books from the library (online digital books) and figured out the solution to the sink between the toilet and vent problem. Just put in another vent!
    I had the extra pipe in there to keep from having the sink between the toilet and the vent but luckily I saw an image that I was able to copy and revise for my layout.
    Here it is, just in case someone else has this issue.
    Name:  Master Bath Plumbing Layout.png
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    Forum Admin, Expert Plumber Terry's Avatar
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    The bathtub is not vented in that picture. The pipe can't go down before the vent. Only the toilet gets that kind of special treatment.


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    Moderator & Master Plumber hj's Avatar
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    The tub is not vented AND it is an illegal "S" trap. The vent next to the tub is "cosmetic" and does absolutely nothing. THe vent between the toilet and sink is also redundant, unless the toilet is more than 6 feet from the sink connection. It looks like something out of a "1930s" book, except that would not have a 3" toilet connection.
    Licensed residential and commercial plumber

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    DIY in AZ emd36's Avatar
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    Quote Originally Posted by Terry View Post
    The bathtub is not vented in that picture. The pipe can't go down before the vent. Only the toilet gets that kind of special treatment.

    The tub in my picture is after the vent, right? How would I reproduce that 2 story drawing for a horizontal 1 story slab drain?
    Should the vent be directly over the trap? (I mean behind it since it can't be directly over the tub drain!)
    Name:  Master Bath Plumbing Layout_2.png
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    Last edited by emd36; 11-16-2012 at 07:57 AM.

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    DIY in AZ emd36's Avatar
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    Quote Originally Posted by hj View Post
    The tub is not vented AND it is an illegal "S" trap. The vent next to the tub is "cosmetic" and does absolutely nothing. THe vent between the toilet and sink is also redundant, unless the toilet is more than 6 feet from the sink connection. It looks like something out of a "1930s" book, except that would not have a 3" toilet connection.
    Thanks for helping me out. The initial drawing may have been from a 30's book, but I'm trying to follow 2009 IPC, so I altered the drawing using cut and paste.
    Is the tub not vented because the vent is connected to the main sewer instead of the trap? (as in Terry's post?) Have I fixed that?
    Although I can see the tub looks like an S trap, the layout is horizontal. Just don't know how to put this drawing into a 3D plane. The 3" wye will be connected horizontally to the drain, reduced to 2", and the trap will be connected to that vertically.
    I understood that for 2009 IPC the toilet can NOT have a wet vent, which means that there can be no fixture between the toilet and the main vent. This distance is about 6' but I saw the solution in a Black and Decker Bathrooms book (2010) that included a vent in between the toilet and the sink, (my sink will be on the toilet side of the vent stack.) I thought this would provide the solution to not having a wet vent for the toilet (?).
    Name:  Screen shot 2012-11-16 at 8.45.19 AM.png
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    How is my plan different from Terry's drawing? (Only one story would apply.) What would I do to create the correct layout of vents and drains in a slab setting?
    Name:  Three vents.png
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    Last edited by emd36; 11-16-2012 at 07:55 AM.

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    DIY in AZ emd36's Avatar
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    Here is the photo of the bathroom pipe being laid out. Not glued yet. The sewer pipe takes a jog back to the vent pipe. so there are two 45's in between the toilet and the vent.
    Name:  Master Bath Plumbing_Small 2.jpg
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    I am planning to cut the pipe to place the sink between the toilet and the vent. I thought I also had to vent the toilet before that wet drain.
    I am trying to follow this condition of the code.
    909.1 Horizontal 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 vent.

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    DIY in AZ emd36's Avatar
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    It appears I can eliminate the "cosmetic" toilet vent?

    Name:  Master Bath Plumbing Layout_3.png
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    DIY in AZ emd36's Avatar
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    I have been mulling over the discrepancies in the information that I have. The requirement to have no fixtures enter the drain except downstream of the vent must be a UPC requirement, I can't find it anywhere in the 2009 IPC.
    Bert Polk's Plumbing Guide clearly states in the Toilet Rough In section:
    4. The closet bend can be up to 6 foot long. No drains from other fixtures may enter into the closet bend. Only down- stream of the vent.
    He has various diagrams showing how this can be done, including one that looks like my "cosmetic" vent. That is a 2" vent down stream of the toilet. Although this one is a 3" vent.
    Name:  Toilet Vent Downstream.png
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    It appears that this would be less effective than a vent branching from the toilet vertical, like this. But I don't think I have the vertical space for a 3" to 2" wye between the sweep and the flange.
    Name:  Toilet Vent 1.png
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    Here is another layout that it looks like I could duplicate from the Black and Decker Guide to Bathrooms.
    Name:  Plumbing Diagram for Basement.jpg
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    And here is an almost identical layout from Black and Decker Complete Guide to Plumbing.
    Name:  Plumbing Diagram Basement 2.png
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    These diagrams are much better than mine, so perhaps they will be easier to critique.
    Thanks...
    Last edited by emd36; 11-17-2012 at 09:41 AM.

  12. #12
    Forum Admin, Expert Plumber Terry's Avatar
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    If you have a pipe on the horizontal below the flood level, the code says it must be a wye fitting or combo fitting.
    Most of the pictures from books that you are showing have santees.

    An inspector would have a good time turning down those drawings.

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    DIY in AZ emd36's Avatar
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    Yes, thanks, I see several connections that look like santees. I know they are illegal used horizontally from the plumbing guide. I took all those that I bought back and purchased wyes. Substituting wyes is not difficult, just require an additional bend in most cases.
    The problem that I'm hearing being pointed out is that the resources I have are not necessarily up to "code". I have the IPC code. Yet it appears that the required venting of a toilet without a fixture in between is not common practice. Thus the reason for advice that says I don't need it.
    The town I have the plumbing permit in uses 2009 IPC without modifications. Here is the paragraph about wet venting.
    908.2 Horizontal Wet Venting for Bathroom Groups.
    908.2.1 Where Permitted. Water closets, bath- tubs, showers and floor drains within one (1) or two (2) bathroom groups located on the same floor level and for private use shall be permitted to be vented by a 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 or trap arm connection to the horizontal branch drain. Each wet-vented fixture drain or trap arm shall connect independently to the wet-vented horizontal branch drain. Each individual fixture drain or trap arm shall connect horizontally to the wet-vented horizontal branch drain or shall be provided with a dry vent. The trap to vent distance shall be in accordance with Table 10-I.
    Only the fixtures within the bathroom groups shall connect to the wet-vented horizontal branch drain. The water closet fixture drain or trap arm connection to the wet vent shall be downstream of any fixture drain or trap arm connections. Any additional fixtures shall discharge downstream of the wet vent system and be conventionally vented.

    I think the statement in bold means that the water closet cannot have a fixture that enters before the vent without a separate dry vent between them OR the toilet has to be downstream of any other fixture connections. Is this the same as the information (number 4) in the plumbing guide?

    I have worked on my drawings more and on a photo of the current replacement plumbing. Maybe they can be more informative for helping me with this project. Thanks!

    Name:  Plumbing from Pic.jpg
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    The tub would be vented in the ceiling to the main vent but drain separately downhill to the 3" main drain using a 2" to 3" wye to connect.
    Name:  Plumbing Diagram for Basement Rev.jpg
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    This drawing seems to show that the recommended connections are wyes, it is hard to see though and they appear to be slanting upstream of the main drain, which is backwards, isn't it? Unless vents are always slanted away from the fixture they vent?
    Name:  Plumbing Diagram Basement Rev.jpg
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    This is the altered pipe drawing to show my layout.
    I could separate the sink drain and run it in a 2" drain past the main vent to connect on the shower side.

    I appreciate all the suggestions.
    Last edited by emd36; 11-17-2012 at 01:40 PM.

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    Forum Admin, Expert Plumber Terry's Avatar
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    In a situation like that, I run the 3" line as close as I can to the wall, and at the last 45 over to the toilet.
    That way I can keep the toilet vent at a 45, which is considered vertical.
    Or you can run the lav in 2" and wet vent the toilet.

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    DIY in AZ emd36's Avatar
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    Hey, that is a good idea to run the 3" against the wall and running 45 at the toilet bend instead of jogging it over. I didn't think I could wet vent the toilet. Yet is seems to be common practice. I might call my inspector and ask. He has really been helpful. Thanks...

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