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Thread: Shower p trap

  1. #1
    DIY Junior Member BGM's Avatar
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    Default Shower p trap

    I'm replacing the acrylic shower in my (concrete slab) basement bathroom with a new one. When I removed the old shower base, I found that the water was draining straight down into a 90 degree elbow and then into a straight horizontal run of pipe (PVC) which leads to the sewage ejector pit, which is about 10 feet away from the drain. My limited plumbing knowledge tells me that there should be a p trap somewhere between the drain and the pit.

    I'm looking for advice on what to do. Option A is to install a p trap directly underneath the shower drain. This would require me to break up some concrete in order for the p trap to be installed in the proper location (12" from the wall) to accommodate the new shower. The horizontal run of PVC, from what I can see, is at least partially encased in the concrete slab. If I were to break up the concrete and not damage the pipe, would the surface of the pipe still be too "rough" to be able to be properly cemented to the p trap?

    The other Option B that I am considering is to add a p trap at the "end of the line" in the ejector pit. I haven't removed the lid from the ejector pit yet to see if this is even feasible, but is this wise?

    I should mention that we have been living here for 4 years, yet never smelled any bad odors from the shower drain. I realize that the lack of smell does not necessarily mean that there are not odorless gases rising through the drain. Just wanted to mention this.

    Also, I tried running electrical fish tape through the pipe to see if I could "feel" if there was a trap somewhere along the line, but it just went in a couple of feet and seemed to hit a clump of hair and stopped. I guess it's just too flimsy. Tonight I bought an auger and I'll try it tomorrow to clear up the obstruction and "feel" for a trap.

    I tried to attach a sketch, but I can't seem to get the file size small enough to post.

    Please give me any comments on my options or alternate suggestions. Thanks,

  2. #2
    Master Plumber Redwood's Avatar
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    Break concrete and install the trap right under the drain.
    You may be hitting a trap installed in the line. this is not right and is called a running trap. The trap will also need to be vented a 10' run to the pit is too long to be vented by the pit.

    How is the pit vented? It needs a through the roof vent.

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    Thanks Redwood, I was afraid that would be the answer. Attached is a .pdf sketch. The sewage ejector pit is vented out through the roof.

    My concern is not so much breaking up the concrete, but will the outer diameter surface of the PVC pipe that was previously encased in concrete be of good enough quality to ensure a sound cemented connection? How can residue (if any) be removed from this surface? Or does the concrete not "stick" to the PVC?

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    Master Plumber Redwood's Avatar
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    I'm not seeing any attachment...

    The pvc should clean up fairly well but if it doesn't a sheilded coupling such as a Fernco Proflex could be used.

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    I'm not sure why it didn't attach...let me try again.

    shower drain.pdf

    Once I've installed the trap, should the opening in the concrete by re-filled in with concrete or an alternate? The opening is currently 12" long x 6" wide.

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    Master Plumber Redwood's Avatar
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    Okay, I see your drawing now...

    You still need to find out if there is a running trap and there is venting before you go any further. You cannot have 2 traps on a line and at 10' in length a vent is needed.

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    Attached is a top view of the bathroom

    shower drain top view.pdf

    I cleaned the drain with an auger and pulled out a bit of hair from it. I ran the auger in about 11', but I still can't really tell if there is a running trap. I feel some resistance, but probably not enough to be a trap. I plan on removing the lid from the ejector pit and shining a flashlight down the drain, to see if I can see any light on the other end. This should tell me if there is a running trap or not. Assuming that there is no trap, it should be easy enough for me to add one, since I also discovered that the 90 degree elbow was not even cemented in place!

    There is no vent for the shower drain. Per code, a 2" drain should be vented within 5' of the trap. Per the attached sketch, this seems impossible, unless I want a vent pipe coming out of the floor in the middle of the bathroom. The only thing that I can think of is to add an air admittance valve after the trap, underneath the shower pan. The shower pan will be butted up directly against the studs (not against drywall), so there should be adequate airflow to not create a vacuum between the floor and the pan. This valve, however, will not be easily accessable.

    Any suggestions???
    Last edited by Terry; 06-20-2008 at 08:51 AM.

  8. #8
    Forum Admin, Expert Plumber Terry's Avatar
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    An Air Admittance Valve needs air. It needs to be in a ventilated space, with access for replacement.

    You could put the vent at the wall. That would be less than five feet from the wier of the p-trap and within code.

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    Sorry, in my previous post I meant to say that per code, a 2" drain should be vented within 4' from the trap, not 5'. So putting the vent on the other side of the wall is not within code either.

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    Master Plumber Redwood's Avatar
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    Where does the Lav Sink drain tie in? It's possible to wet vent with the lav sink.

  11. #11
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    Attached is a side view showing the new shower pan.

    shower drain side view.pdf

    Let's consider the "north" wall to be at the top of my previous sketch. I could run a vent through either the north or east walls.

    My understanding of the code is that the vent must come off of the waste line at an angle of no more than 45 degrees from vertical.

    I'm a little confused as to when a horizontal run of the vent line is allowed. Is it 6" above the flood level of the fixture, or should the vent be connected to the main stack 6" above the flood level of the highest fixture for which the vent serves?

    If the former is true, then the "green" vent in my sketch would be required, which is not feasible since it would go through the shower pan. If the latter is true, then I could squeeze the "red" vent in, and then connect it to the main vent.

    By the way, the sink vent is further south of the toilet, and not feasible to connect to.

  12. #12
    Master Plumber Redwood's Avatar
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    AAAARRRRRRGGGGG! My PC hates opening pdf files.... I've got to get more RAM.

    I'll get back to ya! I'm heading for the lockup zone!

    Actually before I go there... What is the max length allowed under your code for 2". You can tie in at any point along that length. And I believe that you must roll in at 45 or... more! so you could vent closer to the pit and gain additional depth to work with.
    Last edited by Redwood; 06-20-2008 at 02:28 PM.

  13. #13
    Forum Admin, Expert Plumber Terry's Avatar
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    UPC plumbing code is
    1.5, 42"
    2.0" 60"
    3.0" 72"
    4.0 120" unless its for a toilet, then it's 72"

  14. #14
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    Under the Illinois code, the max length for 2" pipe is 4'.

    http://www.ilga.gov/commission/jcar/...ZZ9996aiR.html

    I found a way that might work for my situation.
    shower drain side view - #2.pdf

    I would run the vent from the shower drain as shown with 1 1/2" PVC and connect it in the attic to the vent that serves the kitchen sink. I have two questions:

    1)Is the horizontal portion of the vent under the shower pan OK? Please read section c of the following:
    http://www.ilga.gov/commission/jcar/...00K14500R.html

    2)The horizontal length of vent pipe would be 1' under the shower pan + 12' in the attic = 13'. For 1 1/2" vent pipe and 2" soil pipe, the maximum vent length allowed is 75' and up to 20% of this distance (15') can be horizontal, so I should be OK. Am I understanding this correctly?
    http://www.ilga.gov/commission/jcar/...ZZ9996akR.html

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