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Thread: Drain routing in bathroom remodel

  1. #1
    DIY Junior Member austintx's Avatar
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    Default Drain routing in bathroom remodel

    Hello all,
    I am currently in the beginning stages of a bathroom remodel (half way through demolition) and would appreciate any input on the layout of my drain lines and vents. I am moving the location of the toilet and sink. The tub is being replaced with a shower with a 2" drain line and the toilet is being moved about 3 feet. The sink is also moving a couple of feet closer to the exterior wall. I am on a concrete slab that is not post tensioned. This area this bathroom is in was originally an attached garage that was converted into a bedroom/bathroom, so the plumbing is not original to the house (house was built 1960, add on was done about 10-15 years ago).

    Since I am having to reroute/replace all of the drain lines inside the bathroom, I am going to have to break some concrete. I would prefer not to break any more than is neccesary. If you will note my image below, the green lines are drain lines, and the red ones are vents (this is a single story house). First off, does the routing make sense/pass muster? It will all be sloped 1/4" per foot. There is a 4" drain line outside (top) that the current bathroom pumbing drains into, the new plumbing will tie into this line. Since the sink will be close to the outside wall, my plan is to run its drain straight down throuhg the wall, through the concrete slab, the el to the outside. From there it will then tie into the 4" exterior line. For this drain, I was thinking about boring a 2" hole in the concrete slab to run the 1.5" drain line. Since it is only about 18 inches form the exterior, it would be pretty easy to simply dig from the outside to install the el and remaining pipe.

    I would knock out a trench from the shower drain to the toilet flange, using 2" line (with p-trap of course) for the shower, then connect that to the 3" line for the toilet. For the vents for the shower and toilet, I was thinking about again boring a 2" hole for each and run them up and into the attic. Currently, each fixture has a 1.5" vent that is tied together in the attic, then a single 1.5" vent protruding through the roof. I have heard that newer toilets should use a 2" vent, but have also seen on this forum how a single 1.5" vent could be sufficient. If I could tie all the vents together and utilize the existing 1.5" vent, that would be great. If not, I am willing to do what it takes to build it properly. Thanks in advance for everyone's help!
    Last edited by austintx; 06-25-2009 at 05:25 AM.

  2. #2
    DIY Junior Member austintx's Avatar
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    OK, for some reason the picture doesn't show up, lets try that again...
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    Master Plumber nhmaster's Avatar
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    No vent pipes or portions thereof may run horizontally until they have risen 6" above the flood level rim of the highest branch fixture ( in this case the lav) So as drawn, both the shower and the toilet vent are not good. Additionally, if you are under the IPC code, you do not have to directly vent the toilet. The distance fom toilet to vent is "unlimited"

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    Plumbing Designer FloridaOrange's Avatar
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    This would be code compliant in FL and I believe elsewhere IPC is in effect.
    3" to toilet, 2" to shower, 2" to lav with 2" vent.

    Taking lines outside means going under or through foundations, cutting concrete isn't a big deal.

    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

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    Moderator & Master Plumber hj's Avatar
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    Default Dwv

    You do not show how deep the main sewer line is, nor if any of these walls are over the concrete foundation walls. With enough depth, and no walls there are much better configurations.

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    DIY Junior Member austintx's Avatar
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    OK I get it now. I moved the drainlines so that the vent would rise vertically from it. That also means I would only need 1 vent for the shower and toilet, correct? I am under IRC here.
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    Last edited by austintx; 06-24-2009 at 07:32 AM. Reason: IRC

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    DIY Junior Member austintx's Avatar
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    Scratch my reply above, I did not see your response until after I submitted it.

    As far as the concrete foundation walls, I do not believe they are very deep, perhaps 6" deeper than the foundation slab itself. Outside where my 4" line is, it is probably another 12" down. I will take a picture and some measurements as soon as I get home today.

    From the looks of your diagram, I would only need one vent, at the lavatory?

  8. #8
    Retired Defense Industry Engineer jadnashua's Avatar
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    Vents from multiple fixtures may join into one, but as noted, they must rise high enough first so that they don't become an alternate drain for any of the other fixtures connected to them. generally, this is considered to be 6" above the flood rim of the highest fixture. The other major consideration is the number of fixtures will determine the size of the vent required once they all come together. In cold areas, it may also have to be larger going through the roof so it doesn't get clogged by frost from the rising moist air.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  9. #9
    DIY Junior Member austintx's Avatar
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    I snapped a picture of the drain outside, it is hard to tell, but the top of the drain line in the picture is about 18" from the top of the foundation, the base of the foundation footing is about 4" or so above the top of the drain line, so there is some wiggle room. The thing that is running left to right is actually a tree root.
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    Moderator & Master Plumber hj's Avatar
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    Default Dwv

    If the drain line were deep enough AND the distance from the sink to the shower drain was within limits, I might put the vertical pipe behind the sink and then run an arm to the toilet, using a side inlet sanitary tee, another one to the shower drain. But I would not run the lavatory outside as a separate pipe, unless there is some reason not apparent in your drawing. The way you have it configured, the lavatory probably could not be used as the toilet/shower vent.

  11. #11
    DIY Junior Member austintx's Avatar
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    The only reason I was thinking about running the drain for the lavatory outside as a seperate pipe was that I figured I would cut less concrete that way. Everyone says that cutting concrete isn't that hard, so maybe I am just worrying about that part too much. One thing that I neglected to mention, the current 4" drain pipe form the outside, connects to the bathroom right in the middle of the upper wall. I have not dug enough of the yard up (triple digit weather) to see where the line goes or how far out from the house it is, but I don't except that to be a major issue. I have attached two more layouts based on the helpful information and suggestions you all have provided (many thanks!). This bathroom is only 7' by 7' (roughly), but I have added a vent at the upper wall in these drawings.
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  12. #12
    Moderator & Master Plumber hj's Avatar
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    Default vent

    That vent in the wall by the toilet is strictly cosmetic, it does absolutely NOTHING to improve, or degrade, the plumbing system.

  13. #13
    DIY Junior Member austintx's Avatar
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    OK, so the 2" vent at the lavatory would be sufficient. besides that, would either of the two layouts above be correct?

  14. #14
    Plunger/TurdPuncher kingsotall's Avatar
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    Drilling concrete is not that hard...if you have a rotary hammer and preferably core bits. Although punching a bunch of smaller holes also works. But mind you these are specialized tools. The bigger the tool the better, too.
    I just post cuz I like to see my avatar.

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    Plumbing Designer FloridaOrange's Avatar
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    Both are correct, I usually design to take the largest pipe straight towards it's fixture, the toilet in this case, but that's a matter of preference.

    If the wall that the lavatory is going on is a frame wall then you can head straight to it and branch over in the wall for the trap, again that's a matter of preference.
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

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