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Thread: venting in slab

  1. #1

    Default venting in slab

    Another venting question. I wish I had a picture for you but I hope my description is enough. Here's the situation. I am installing a bathroom in my basement. I have removed the old floor drain in the corner that fed via a short section of clay pipe to the 4" line to the aeration system outside. The 4" line enters under the footer and immediately connects to a 4x4x2 wye with 45 facing up to serve as the drain for a sink. The sink is about 3' from this drain but I will probably vent it separately above the trap.

    Extending straight out from the 4x4x2 wye is the toilet location, about 18" from hub of wye to center of closet flange. I have sized down to 3" out of the fitting with a bushing. If this were all then I could use the sink drain as a wet vent, but there is also a shower next in line, then a drain from the upstairs kitchen, then the washing machine standpipe, the a floor drain. All of the fixtures from the shower to the floor drain will have their own vents connected in the wall 6" above the bathroom sink and a single 2" vent will rise to the first floor and connect in to the kitchen vent pipe 6" above the sink. My question is what is the best way to branch off of the drain for these additional fixtures. Here are the options I am considering:

    1) between first wye fitting for sink drain and closet bend I install a wye fitting leading to the other drain locations. This would leave me no room to separately vent the toilet. The sink would be the wet vent but my concern is the other wye in between. Would this be allowed. I could install a vent tee turned up after the second wye fitting for the additional drains but it seems that this would be no better than using the sink drain as a wet vent.

    2) instead of a closet bend for the toilet I install a long sweep wye. I have plenty of depth for this. This would allow for a vent tee in between the sink drain wye and the toilet. I would then continue on to the other fixtures venting each as noted above.

    It seems ideal to me to vent each fixture arm between the trap and the connection to the main line but space just doesn't permit. Sorry to be so long winded. Someday I'll learn to post drawings.

    Scott

  2. #2

    Default Picture

    I'm sure a picture will help. All the distances are quite close between fixtures. Any suggestions?

    Scott
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    Last edited by hefty4690; 03-10-2009 at 07:08 PM. Reason: Changed picture

  3. #3
    Master Plumber nhmaster's Avatar
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    If those vents for the shower and floor drain, run horizontally under the slab it will not be legally vented. No part of the vant may run horizontal until it is 6" above the flood level rim of the highest fixture served. There appears to be 2 vents for the lav ? The toilet does not need to be vented.

  4. #4

    Default Vents

    Thanks nhmaster

    Ok so I can remove the vent coming up from the sink trap or the wet vent portion. Critical distance isn't a problem so I guess it doesn't matter which one I remove does it?

    How do you suggest that I vent these pipes in the slab? Will I need to route my horizontal drains so that I can I can point a tee straight up into the wall, say next to the shower? This will be more of a challenge due to space limitations but I want it right. I didn't take the time to put the walls in my picture but the toilet is in a 30" nook between the exterior wall and the shower wall. The shower stall is 36". The standpipe will go in the right wall of the shower and the floor drain will go 3' or so further than that. Could I run 3" to the base of the standpipe and then on to the floor drain, using a 2" vent for the standpipe to wet vent the floor drain or does it require it's own? I thought that the vents could come off the drains in the slab as long as they were tilted 45 deg or greater and sloped up toward the wall where they would then go vertical. I trust you guys though.

    Scott
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  5. #5
    Master Plumber nhmaster's Avatar
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    that works

  6. #6

    Smile Thanks

    So just to be sure, my bottom picture will work with the floor drain vented through the standpipe wet vent. That will save me a little time.

    Scott

  7. #7
    Master Plumber Redwood's Avatar
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    The vent for the shower...
    Is that 1 1/2" below the slab?
    2" is minimum underground.

  8. #8
    Master plumber Jay Mpls's Avatar
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    MN code gets us ...
    the floor drain can be 25' from a vented line,and your min. waste underground is 2".
    It does not say the minimum *venting* underground is 2".
    We have to get and individual vent on that toilet before it hits the main.
    Good luck hefty.Where are you located?

  9. #9

    Default

    I am in Illinois Jay. I though I might need a separate vent on the toilet but the spacing is so tight. After the main enters the house there is an immediate wye w/ 45 for the sink drain. From the outside of the hub to the center of the toilet flange is only 18". I cannot fit another 3x3x2 wye inbetween the two. Would it be possible to use some sort of wye with a side inlet for the closet bend? nhmaster will surely make his point about horizontal venting in the slab though. Nothing on this 5+ year house remodel has been smooth and I guess that is why I have learned so much. But I sure would have liked for the main to enter just a little to the left or right of where it is. Any ideas on close quarters connections would be great.

    Thanks, Scott

  10. #10

    Default toilet venting

    Here is a new drawing. I have very limited horizontal space to insert a vent for the toilet between the closet bend and the main. I do however have enough vertical space to insert a vent tee between the closet bend at the bottom of the trench and the top of the slab. This vent would run horizontal for about 18", but not flat horizontal, I can probably get 22 deg upward pitch to the exterior wall. Is there any reason that this will not work, or more specifically that it is against code? How else do you vent a toilet on a horizontal main if the branch pipe does not come directly under a wall?

    Thanks again. The inspectors around here I have found are not that strict. I spend a lot of time making things above code and they usually don't even notice. I want to do things right regardless of who looks.

    Scott
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  11. #11

    Default best option

    So it appears that there is and always will be some disagreements on horizontal venting. nhmaster, in your opinion it seems as though I am ok not to vent the toilet separately but others say that it is necessary. The toilet is 18" from a vent wet vent. Other than digging back under the footer and splitting off the main sooner I do not have room for a separate vent on the toilet. Like I said in a previous post I do have room in the horizontal piping to the toilet to install a tee and possibly even a wye with a very short (17") sloped horizontal vent to the wall. I cannot see how this would cause a problem. I am ready to start installing pipe but will not do so until I am convinced that I am doing it right.

    Thanks, Scott

  12. #12
    Illinois Licensed Plumber SewerRatz's Avatar
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    If you are in Illinois the smallest pipe you are allowed to use under ground is 4" pipe. Water closet must have its own vent tied in after the closet bend rolled off the top with a 4"x2" wye then vented to the nearest wall.

    Your best bet is to draw up your plans and take them to your local permit office and have the plumbing inspector approve them. I would also get a permit as well, if you get caught doing this work with out a permit the fines in Illinois are very hefty. Also double check with the inspector their are parts of Illinois that do not allow PVC under ground, and there are still parts that do not allow PVC to be used in drain systems that have metal pipes. I know they make fittings and such to transition from PVC to steal, CI, or even copper, but them are the rules in that town.

  13. #13
    Illinois Licensed Plumber SewerRatz's Avatar
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    Default From Illinois Plumbing Code Book

    Section 890.1340 Determination of Sizes for Drainage System

    a) Maximum Fixture Unit Load. The maximum number of drainage fixture units that may be connected to a given size of building drain, horizontal branch, or vertical soil or waste stack is given in Appendix A: Tables G and H.

    b) Minimum Size of Building Drain, Horizontal Branches, Drainage Piping
    1) The minimum size of any gravity building drain shall be four (4) inches in diameter.

    2) Pressure building drains shall not be used where gravity drains may be installed. Pressure building drains shall be sized in accordance with the ejector pump manufacturer's recommendation but shall not be less than two (2) inches in diameter.

    3) Gravity drained horizontal branches of the building drain shall be sized in accordance with Appendix A, Table H.

    4) No portion of the drainage system installed underground or below a basement or cellar shall be less than two (2) inches in diameter.

    5) The drainage piping shall not be reduced in size in the direction of flow.
    c) Minimum Size of Soil and Waste Stacks. No soil or waste stack shall be smaller than the largest horizontal branch connected thereto except that a four (4) inch x three (3) inch water closet connection shall not be considered as a reduction in pipe size.

    d) Waste Stacks Serving Kitchen Sinks. In one (1) or two (2) family dwellings in which the waste stack or vent receives the discharge of a kitchen-type sink and also serves as a vent for fixtures connected to the horizontal portion of the branch served by the waste stack, the minimum size of the waste stack up to the highest sink branch connection shall be two (2) inches in diameter. Above that point the size of the stack shall be governed by the total number of drainage fixture units vented by the stack. (See Appendix J: Illustration F.)

    e) Future Fixtures. When provision is made for the future installation of fixtures, those provided for shall be considered in determining the required size of drain pipes and vent piping during initial construction. Piping provided for such future installation of fixtures shall be terminated with a plugged fitting or fittings at the stack so as to form no dead ends. In a multi-story building, when openings are roughed in for future fixtures below the uppermost level, properly sized vent piping shall be connected to the vent system and carried down to the appropriate lower level and be capped or plugged in an accessible location for venting of the future fixtures.

  14. #14

    Default got shovel?

    Thanks sewerratz, I think. How close are you to Fairview Heights and do you own a shovel? It looks like I am going to have to cut out the wye that I reduced to 3" under the footer. Any recommendations for cutting 4" pvc when I cant get a sawzall in there?

    If I cut it back far enough I may be able to produce enough room to roll off a wye in the horizontal toilet drain. If not do you think that there would be a problem installing a vertical wye in the riser for the vent as shown in my last picture.

    Also, should I use 2" min for all pipes entering the slab? It sounds that the code addresses drain pipe but not necessarily vents.

    I am going to pull a permit for this work. I know some friends locally, although in an area known for being unreasonable, that redid their entire basement without a permit and it was a headache when the inspectors came in before they sold it and knew that it had been done. They are good friends that we go to church with and they put themselves in a position where they were running back and forth to Lowes to color match stain to pressure treated green. That's sad to me. In their defense her father did most of the work and he is "always right".

    Scott

  15. #15
    Illinois Licensed Plumber SewerRatz's Avatar
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    Default

    2" for all the branch drains is correct. so venting has to stay 2" as well.

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