Under basement slab: should I assume there's a trap or do I need to install?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by IndyGopher, May 22, 2020 at 2:11 PM.

  1. IndyGopher

    IndyGopher New Member

    Joined:
    Apr 7, 2019
    Location:
    Indianapolis
    Plan to install a shower and freestanding tub in my basement. When I peeked in the boxes, I saw only horizontal capped 2" lines rather than p-traps. Is it typical to embed the traps in the slab after municipal inspection or should I assume I need to install traps? Or are you going to tell me the only way to find out is to open that pipe and run something through it?

    If there are traps, should I be worried about how far they potentially are from the drain? I thought long horizontal runs before traps was a bad thing due to possible accumulation of gunk.

    Thanks for opinions!
     

    Attached Files:

  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    Since the exact location of the trap and riser is dependent on the tub or shower you install, it would be kind of foolish to install the trap during the initial install of the trap arm. Now, whether they really have that line vented properly or not, you hopefully will see that pipe sticking up. On a 2" line, that must occur within five feet of the trap under the UPC code (further on IPC).
     
    Jeff H Young likes this.
  3. Sponsor

    Sponsor Paid Advertisement

     
    Jeff H Young likes this.
  4. IndyGopher

    IndyGopher New Member

    Joined:
    Apr 7, 2019
    Location:
    Indianapolis
    Thanks for the quick reply, Jim. So I'll be installing traps at these drains. Got it. As for venting, my understanding is that everything is wet vented under the slap to dry vents off the two lavs we've got in the bathroom. The builder left two capped vents in the ceiling for those, so it's my plan anyway...
     
  5. hj

    hj Moderator & Master Plumber Staff Member

    Joined:
    Aug 31, 2004
    Occupation:
    Plumber
    Location:
    Cave Creek, Arizona
    You CANNOT "assume" about traps. If you do NOT have one you have to install it, but if you DO have one you CANNOT install another one.
     
    IndyGopher and Jeff H Young like this.
  6. Jeff H Young

    Jeff H Young Active Member

    Joined:
    Feb 27, 2020
    Location:
    92346
    I dont like to assume too much but if there isnt a trap in a tub box why would you suspect a trap? probebly no vent nearby either.
    Is this a rough in for future bathroom that was already in house? And heck yea id run a tapemeasure or fish tape something down it . it wouldnt be smart to just build a bathroom only to find out later it was plugged with concrete 4 inches away. I know you think you are describing this well but the pic dosent tell a lot . No idea if its wet vented or not let alone properly the vents in the cieling would need to connect with something. But your basic question as to whether they would put a trap on typicaly? I would say no not typical To put a trap on something that you as a builder or plumber have no intention of completing just cap the end would be typical, also if there was a trap it should be in the box
     
    IndyGopher likes this.
  7. Jeff H Young

    Jeff H Young Active Member

    Joined:
    Feb 27, 2020
    Location:
    92346
    ok a little more info Those could be very simply 2 inch drainlines not vented at all just futures under slab. But Im not psycic it would take a quick look around to get an idea. also id suggest run a hose down full blast for awhile befor calling it good
     
  8. IndyGopher

    IndyGopher New Member

    Joined:
    Apr 7, 2019
    Location:
    Indianapolis
    Thanks a bunch for these additional replies this morning! Sounds like it's unlikely there's a trap further down the line under the slab, but I'll cut off the cap and run a tape measure through just to be sure.

    As for venting, the builder knew the exact bathroom plan when laying plumbing under slab (the placements were all customized for future finishing). They tell me it's wet vented properly to lavs which will be vented to capped lines in the ceiling directly above. I can't be sure of that because I didn't see the plumbing before the foundation was poured, but it makes sense given what was left for finishing. I posted more pictures of the whole basement set up (2 bathrooms and a bar) in a thread a couple months back that didn't get much action, so I'd welcome any opinions based off that. https://terrylove.com/forums/index....-a-basement-with-2-bathrooms-and-a-bar.86682/

    Thanks again!
     
  9. Jeff H Young

    Jeff H Young Active Member

    Joined:
    Feb 27, 2020
    Location:
    92346
    Ok great so you must have verticle pipe coming thru slab for the lavs that serve as vents
    It looks good went to other thread terry had good advice . So I fully expect you need the trap . the other pictures helped a lot !
     
    IndyGopher likes this.
  10. WorthFlorida

    WorthFlorida The wife is still training me.

    Joined:
    Oct 28, 2009
    Occupation:
    Retired
    Location:
    Orlando, Florida
    How old is this home and what was or is this box used for?
    A floor drain into a sump pump? If yes there be no trap anywhere.
    Why is there water in it?
    Do you know where this pipe leads to?

    It must end up to the septic line or street sewer. Traps are always at the floor drain or fixture. Old homes before the 1960's had cast iron pipe and a 4" trap was installed where the pipe led out of the home. It is no longer required and can be removed.
     
    IndyGopher likes this.
  11. IndyGopher

    IndyGopher New Member

    Joined:
    Apr 7, 2019
    Location:
    Indianapolis
    @Jeff H Young : Thanks for taking a look at that other thread and confirming what Terry said! I'll expect to install traps at each drain, but I'll still double-check the interior of the pipes with a tape measure or something just to be sure.

    @WorthFlorida: Thanks for checking in. The house is one year old and the pipes all lead to an in-floor basin where a sewage pump will be installed. That will pump to the main sewer line. The plumbing was all roughed-in to spec knowing that the basement would eventually be finished with 2 bathrooms.

    As for why there's water in the box, I have no idea. This is my first time opening one of these, so is that unusual and/or very bad? I can reach out to my builder if there might be some huge issue. Anyone?
     
  12. Jeff H Young

    Jeff H Young Active Member

    Joined:
    Feb 27, 2020
    Location:
    92346
    didnt notice water but the boxes are watertite although they do crack and have nock outs and can easily leak water in around the pipe, Basements here are so uncommon to me but as a young kid we had a basement and lived in conneticut I remember moppping out water.
    Any dampness in that box with a top box would be somewhat trapped . So since I dont even know a person with a basement Id be looking for sighnes of water coming in from the ground, grade arround the property, but I always look at that stuff. I think its a typical concern but might not be a typical problem .
     
    IndyGopher likes this.
  13. IndyGopher

    IndyGopher New Member

    Joined:
    Apr 7, 2019
    Location:
    Indianapolis
    Thanks again, Jeff. You've been beyond helpful. I feel a lot more confident about this thanks to you and everyone else who replied. The water table here in Central Indiana is extremely high, so I'm guessing it's groundwater that leaked in at cracks in the box and the opening around the pipe this past year. I don't see any signs of moisture in the basement -- floor or otherwise -- so I'm hopefully OK. Just didn't want to go ahead with finishing this up and cementing around that pipe if the water was a huge red flag to anyone.
     
  14. WorthFlorida

    WorthFlorida The wife is still training me.

    Joined:
    Oct 28, 2009
    Occupation:
    Retired
    Location:
    Orlando, Florida
    A one year old home and if it is a a new development, it takes awhile for the groundwater to drop. If there are little or no established lawns, the water has nowhere to go but down and until the soil packs around the foundation a lot of water will run down the wall into the french drain. That water is probably seeping in from under the slab.

    I had new homes in Algonquin, Illinois and Syracuse, NY and it took about a year before the water slowed up from dumping into the sump pump. During a rain storm it sometimes sounded like a spigot was open echoing from the pit.
     
    IndyGopher likes this.
  15. IndyGopher

    IndyGopher New Member

    Joined:
    Apr 7, 2019
    Location:
    Indianapolis
    Ha, yeah you described my situation perfectly. One year new construction with surrounding homes no more than 2 or 3 years old. My sump pump works overtime after heavy rains for sure.
     
Similar Threads: Under basement
Forum Title Date
Plumbing Forum, Professional & DIY Advice Help me understand venting in a basement with 2 bathrooms and a bar Apr 4, 2020
Plumbing Forum, Professional & DIY Advice Under counter water filter in basement Mar 28, 2020
Plumbing Forum, Professional & DIY Advice Why would PVC pipe break under basement floor Dec 26, 2019
Plumbing Forum, Professional & DIY Advice Broken Drain Under Basement Floor Sep 6, 2018
Plumbing Forum, Professional & DIY Advice Basement under slab waste pipes Jun 18, 2018

Share This Page