Question on Draining Disposer

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by same2you, Jul 29, 2010.

  1. same2you

    same2you New Member

    Messages:
    7
    Location:
    Toronto
    I'm about to change the counter/sink/etc in my kitchen and would like to install a disposer. Unfortunately, the sink that was chosen has the smaller sink on the right, and that is where we want the disposer, but the current setup has the drain going into the floor on the right side of the cabinet (then along the ceiling in the basement to the main drainpipe). I've included a diagram of what the currnet layout is (not even knowing if it is code), and was hoping if someone could provide some advice on how to setup the drain with the disposer installed on the right side.

    current.jpg

    (Red line is the floor)

    There's a drop ceiling in the basement, so it is easy enough to move the drain to the left side if needed... but should the P Trap remain in the ceiling below moving forward? Should the entire setup be changed?

    Thanks!
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,487
    Location:
    Cave Creek, Arizona
    Most inspectors, and plumbers, would say to change the entire system and put the trap inside the cabinet where it belongs.
  3. Redwood

    Redwood Master Plumber

    Messages:
    7,453
    Location:
    Connecticut
    Canada does have some strange code sections that allow the configuration you have...

    I guess I like ours better where the trap would be in the cabinet...
  4. same2you

    same2you New Member

    Messages:
    7
    Location:
    Toronto
    So something like below would be the best way to go?
    Changed.jpg
  5. shacko

    shacko Master Plumber-Gas Fitter

    Messages:
    561
    Location:
    Rosedale, Md
    If you add a vent to it, what you have is an s-trap, a no no.
  6. same2you

    same2you New Member

    Messages:
    7
    Location:
    Toronto
    ok then... it look like the easiest way for me to do this is to stick with our goofy Canadian code, but move it to the left (pictured below)... unless someone has a better idea to retrfit it (note that I will NOT be able to access the wall in behind the cabinet as it is brick (townhouse firewall). Just one more question... how much of a slope should I introduce into the horizontal connection between the disposer and the left sink (in blue)... if any?
    same old.jpg

    Cheers!
  7. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,328
    Location:
    Yakima WA
    Minimum slope for a drain is 1/4" per foot. On a very short distance you don't have to get too precise, but definitely it must slope down.
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,892
    Location:
    New England
    The disposal will act as a pump, and you want a baffel between the two sinks to prevent the disposal from pumping crud up into the other sink. If the sink does not have a vent, then I would move the p-trap to the cabinet and add an AAV off the arm to do the best you can with it.
  9. Redwood

    Redwood Master Plumber

    Messages:
    7,453
    Location:
    Connecticut
    Check to make sure that AAV's or Cheater Vents are allowed by code in your area.
  10. same2you

    same2you New Member

    Messages:
    7
    Location:
    Toronto
    I actually have what I believe is a vent further along the line in the basement ceiling (2nd ABS Pipe ties into the drain at a reverse angle then goes verticle), so couldn't I tap into that as a vent as shown in http://www.terrylove.com/forums/showthread.php?1495-Basement-rough-in ? So NOW... it would look like this...

    Vented.jpg


    And actually.... in looking at this... should I completely remove the vent from its current location in the ABS before connecting it inside the cabinet, or can I leave it connected in both locations? I assume that it shoudl only be connected once (unlike how it's drawn) but hey... I'm the guy that was going to introduce an S Trap earlier on ;o)


    (now I can see why plumbers charge so much ;o) )
    Last edited: Jul 29, 2010
  11. Redwood

    Redwood Master Plumber

    Messages:
    7,453
    Location:
    Connecticut
    You are trying to make a loop vent but the p-trap is in the wrong place,

    I was on a Canadian forum just the other day and they said loop vents aren't allowed there..
  12. same2you

    same2you New Member

    Messages:
    7
    Location:
    Toronto
    ughhh....

    So is there a solution to this (besides moving to a new house) that would be within the ability of a guy that's handy?
  13. Redwood

    Redwood Master Plumber

    Messages:
    7,453
    Location:
    Connecticut
    what you had in post #6 is probably the thing to do
  14. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,487
    Location:
    Cave Creek, Arizona
    Do NOT even try to pipe it like you show in that drawing with the blue lines. There is so much wrong with it, that I wouldn't know where to start, and it would be "impossible" to make THAT system correct. IF they allow "P" traps under the floor, I would thing an AAV would be an improvement.
  15. same2you

    same2you New Member

    Messages:
    7
    Location:
    Toronto
    ok, no worries there. So assuming that I am moving forward with a setup similar to post 6, where would I put the AAV? I've read that it has to be installed higher than the drain, but beyond that I just don't know. Also, if I do install the AAV, should I disconnect the vent that is already connected to the line in the basement?

    Sorry for all the questions...
  16. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,892
    Location:
    New England
    Since an aav can eventually wear out, you need to put it where it can be replaced when the time comes. It should go off the trap arm, as high up under the counter as you can get it and still unscrew it to replace without cutting things. Leave the existing vent. An AAV is a one-way air valve that will (or should!) only let air in. The whole goal of any vent to to prevent other draining operations from sucking your drain dry. In this case, the AAV would open to let air in, rather than sucking the trap dry. A full atmostpheric vent can also allow air to escape, like when you are draining a lot of water which can push air ahead of it. All of that is one reason why slope, trap arms, vents need to be installed properly, or stuff doesn't work well in the long-term.
  17. Redwood

    Redwood Master Plumber

    Messages:
    7,453
    Location:
    Connecticut
    I would check your Ontario Code...

    I Believe they will not allow aav's either...

    If they do you would eliminate the trap under the floor and pot in something like this coming up with the p-trap connecting into it.

    [​IMG]

    But I'm pretty darn sure what you will be doing is duplicating what you have moved over slightly.
  18. same2you

    same2you New Member

    Messages:
    7
    Location:
    Toronto
    Looks like Ontario is ok with the AAV provided that it is not feasable to use a conventional vent. So, just to make sure that what I am thinking in my head is what you are also thinking, here's another (and hopefully last) drawing...
    AAV.jpg
  19. Redwood

    Redwood Master Plumber

    Messages:
    7,453
    Location:
    Connecticut
    7.5.9. Air Admittance Valves

    7.5.9.1. Air Admittance Valve as a Vent Terminal
    (1) Individual vents may terminate with a connection to an air admittance valve as provided in Articles 7.5.9.2. and 7.5.9.3.

    7.5.9.2. Air Admittance Valves
    (1) Air admittance valves shall only be used to vent,
    (a) fixtures in buildings undergoing renovation, and
    (b ) installations where connection to a vent may not be practical.
    (2) The air admittance valves shall be located,
    (a) above the flood level rim of the fixture it serves,


    Given that the trap below the floor is allowed and is vented per your code an AAV in this application would not be allowed.

    Also if it were allowed the AAV would have to stick up out of the counter above the rim of the sink.
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