Adding a shower drain to old concrete

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by bs1231, Jan 26, 2008.

  1. bs1231

    bs1231 New Member

    Messages:
    10
    Thanks in advance for your advice. This house is 4o years old.

    I have read through the forums and I have a fairly good idea of what I'm up aginst. I'll be cutting the concrete and adding a drain into my existing waste line. I want to understand the venting and/or if I need to tie into the existing vent.

    The new shower drain will be 24" from the 4" waste line (from upstairs baths).
    The new shower drain is 48" from the existing vent.(behind the toilet)

    I am wondering if I need to tie into the existing vent or not.

    The picts explain it best.

    Thanks!

    Attached Files:

  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,948
    Location:
    New England
    As U understand it, you can tie the new shower drain vent and any others in that room together above the flood plane of the sink (nominally 42"), then run it up to the existing vent, but it has to be above the height of the things that drain. What you don't want to do is what is called wet vent - tie new vents into a drain line and call it a vent when it could be full of waste from things above. You want your new vent line to be connected to a point in the system where it should be dry - i.e., above the flood plane of the other things that may drain into the line.
  3. loop it back to the lav vent

    the only thing in that pic that looks nasty is
    tearing up the concrete...

    also.....you might run into a surprise when you
    cut up that floor...because you dont know
    where the drain line goes and in what direction..
    or how deep it goes too

    Also note....it acutally might be much , much easier to get into the toilet arm
    and branch off from there and revent the line than to
    dig half way down to china looking for a spot to tie into
    that cast iron line.....

    I have literally been in tears before trying to find a spot to tie into
    a cast line....because it was all tight with close hubs and I
    was going to about have to tear up the whole bathroom or
    dig down to China to find a good spot.....


    in either event , all you have to do is to tie into
    the main cast line as best possible and run a
    re-vent back up to the lavatory vent above the lav
    if you can get access.....

    or an auto air vent will suffice if you live in an area with
    more relaxed codes..

    personally I would attack the toilet arm for the easiest
    way to get a 2 inch drain for your shower..
    cause you will most likely end up having to take up the toilet anwyay.



    have fun fun fun................

    http://www.weilhammerplumbing.com/bathroomremod/
    Last edited: Jan 27, 2008
  4. bs1231

    bs1231 New Member

    Messages:
    10
    Ahhh Thanks for the input!

    I do know that the 4" line coming down is the elbow end heading out to the septic past the toilet. But you are right, I'm guessing how far down it goes and I don't even know what to look for to tie a 2" drain to the cast. Sounds like it could be ugly.

    So what you are saying is put a wye between the toilet and the main trunk out? So I would run 4' of 2" from the shower and attach to that wye. And yes the toilet is out-a-here. Need a new one. I can access anything in the wall. I have a lot of sheetrock work to do (later).

    The vent part is confusing to me. Is the shower not vented if I attach to that toilet line (distance:4 feet)? The toilet is vented. If it is not, I would need to add the vent 2' from the shower drain (up next to the 4" line and over to the vent line)?

    I don't know what an auto vent is, but I will find out.

    Thanks!

    This forum is awesome.:D
  5. its no big problem

    If you tear up that floor you will probalby find
    whrer their is a 3x2 or 4x2 wye in the line going to the lavatory down in the concrete

    the easy way is to simply cut that toilet arm back as close to the stackas possible and just re run the toilet arm
    putting in a double wye or whatever ei necessary to
    tie in the old lavatory and new shower unit.....

    figure out where you want to put a shower wall at and
    simply take a vent pipe up that wall.....

    the trap for the hsower is easy to do

    the hardest thing is breaking up the concrete......


    just dont go on a digging safari
    looking for the end of that
    main stack..... its not worth it...
  6. bs1231

    bs1231 New Member

    Messages:
    10
    follow-up

    OK, here's where I'm at now. I'd like to hear if this is a good way to go. I am going to rent a soil pipe cutter to score and crack the cast in front of the bell. I've got a 4" mission no-hub coupling (cast iron to plastic) to a 4x4x3 dwv comb. go up with the 3" to a new clean-out and to another mission coupling attaching to the copper. For the shower, I have a 4x2 flush bushing to the shower ptrap. I understand to put a pitch of 1/4" for that 2 feet.

    I'm trying to justify not installing a vent. The 3" copper is vented right above, and the toilet has a vent. 2 vents within 4 feet of the new ptrap. Do I just wait and test, or should I absolutly install one?

    I understand the concept of having the vent, I just don't understand if I need one or not.

    I could run a 2" tee, close to the flush bushing and add a few 90's zig-zaging over and up to the toilet vent.

    Also, my shower drain will be a kerdi. I assume, from the ptrap straight up I will (for now) have it sticking up 4-5 inches above the (concrete patch) floor. After the new concrete patch is in, and ready for screed, I'll chop it down and install?

    Thanks!
    Brad

    Attached Files:

  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,948
    Location:
    New England
    You need a vent between each trap and any other trap or outlet on the drain line. In that last picture, it appears that the shower line connects to the el for the toilet...when the toilet is flushed, it will suck the trap for the shower dry without a vent line in between.
  8. Terry

    Terry Administrator Staff Member

    Messages:
    14,943
    Location:
    Bothell, Washington
    Don't forget to add the vent between the stack, and the trap.
    The vent prevents the trap from siphoning dry when someone flushes a toilet upstairs.

    The vent can be cut in by installing a combo on it's back, and revented into the toilet or lav vent.
  9. bs1231

    bs1231 New Member

    Messages:
    10
    Final inspection

    Thanks guys for the vent info. Awesome!

    Here is my final product. I vented back around the 3" stack to get to the toilet vent, and put 45's between the stack and the trap. After reading other threads, I tried to get the trap as close as possible to the surface, the 45's helped to do that.

    Anything else?

    Thank you all for your help.

    This forum is amazing.

    Brad

    Attached Files:

  10. fidodie

    fidodie New Member

    Messages:
    94
    Location:
    new jersey
    i think you created an s-trap with the 45s - rather than a p-trap ? the vent would need to be before the 45 bend down (or use a san t to make the turn with a long sweep 90 ? might be able to go hubless san-t to 90. )

    i'm sure the 'real plumbers' will check me on this.

    also, i don't think you need the trap near the surface - if you are covering it with concrete, then the trap should be below the bottom of the concrete (below the plastic)

    an 8" drop to the trap won't hurt anything.
  11. Terry

    Terry Administrator Staff Member

    Messages:
    14,943
    Location:
    Bothell, Washington
    The trap arm for the shower needs to come straight out, not with fittings that raise it up.

    The Santee on it's back will work on the vent, an inspector would like to see a combo there.
    It depends on your inspector, on the fitting.
    The trap arm needs to be straight though.

    [​IMG]
    Combo

    [​IMG]
    Santee
    Last edited: Feb 6, 2008
  12. bs1231

    bs1231 New Member

    Messages:
    10
    OK. Got it.
    I didn't use the combo on it's back because it brought me up too high.

    I trust your opinion, but not quite sure what the problem is with the 45's. Nothing is going uphill, I just 45'd down out of the trap.

    It probably just looks like it because in the picture the assly is tilted to the right as it lays on the concrete?

    But since I am am a learner, I will lower the trap and run a straight (1/2" drop) line to the stack.

    God Bless ya!
  13. bs1231

    bs1231 New Member

    Messages:
    10
    OK. I lowered the trap as instructed, and took out the 45's. Trap now sits 13" down from the concrete floor.

    Thanks Again Everyone!

    Brad
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