Replies

1. 
   Davo304 | May 18, 2003 06:46am | #1

   Although I'm not a plumber, double sinks are connected so that one sink drains over to the other sink, and that sink contains a P trap. There is only one P trap set-up; not two. As for drum traps...I thought they were no longer code approved...at least in new plumbing; because such a system does not vent

   If you are able to install a P trap, I would do so.

   Davo

1. 
   Wet_Head | May 19, 2003 01:15am | #8

   please watch your advice.  he is not speaking of a double sink at all.  he is speaking of 2 individual units.  your advice is 100% incorrect for his situation.

   nothing personal so relax.  just wanted to help out.

2. 
   rasconc | May 18, 2003 07:06am | #2

   I did my double sink with two traps.  When one drains it siphons the other which surprises me.  You would think that a short run to the vent with 1 1/2 pipe would not siphon.  Believe you should run together then trap.  I may add an air admittance valve to fix it as I have a cleanout at the point they join.

1. 
   Davo304 | May 18, 2003 08:46am | #3

   Rasconc,

   The reason for the siphoning is exactly the reason why you shouldn't use individual p traps on a double sink. This technique is against code. Change your sink so that both sinks drain only into a single P trap, and your problem will be eliminated.

   Davo

1. 
   rasconc | May 18, 2003 04:13pm | #4

   Thanks.  It does not siphon enough to empty, it just gurgles. 

2. 
   jelio | May 18, 2003 09:13pm | #5

   Thanks for the advice.  I did not realize the exposure to siphons.  I will plumb one sink over to the other and put the trap below the T.  Should the T be a T-Y? 

   Will the PVC give enough to provide the 1/4" pitch? 

   What is the principle that prevents the drum trap from venting and permits the P-trap to vent ok?  The vanity drain being replaced had the drum trap solution, perhaps because it was installed in '89?

1. 
   Snort | May 19, 2003 12:48am | #6

   I have a bank of drawers between my sinks. Each has a p-trap. No siphon/gurgle. They are vented, through the above attic floor, toa studor vent. Does the venting distance, perhaps, cause the siphon? EliphIno!

1. 
   Wet_Head | May 19, 2003 01:18am | #10

   yours is right.  he was speaking of a double sink.  your's isn't a double sink.  it is 2 separate sinks.

2. 
   Snort | May 19, 2003 01:22am | #11

   Good, I'd hate to have to call my plumber on a Sunday night<G> EliphIno!

3. 
   jelio | May 19, 2003 03:48am | #12

   You are correct, the vanity is not a combined double sink, it is a pair of sinks about 30" apart in a 61" vanity top.  The are located on centers about 15" from each end.

   From your comments, it appears that I should be using 2 separate p-traps.  Correct?

   What prevents the siphon issue described in the previous responses?

   Can the two p-traps dump into a common pipe and travel about 8 feet to the main vent stack?

2. 
   Wet_Head | May 19, 2003 01:13am | #7

   you have e-mail.  be sure to read it!

3. 
   Wet_Head | May 19, 2003 01:17am | #9

   where does any code say you can't drain a 2 compartment sink into 2 p-traps?  I want the section so I can look it up.

1. 
   Davo304 | May 19, 2003 08:49am | #13

   Wet Head Warrior.

    As I first mentioned in my initial posting, I am not a plumber by trade. You're the plumber, not me. I don't have the Uniform Plumbers Code book, so perhaps double P-traps on a double bowl fixture is permitted, but everything I have read and seen in the field does not point to that. Normally, I see one bowl draining into the other and that bowl is connected to a P-trap.  What I have seen depicted in various remodeling books is that 2 traps should not be hooked up to the same arm; nor should they be hooked up in serial...and I may be 100% wrong here ( so please correct me if I am) but I always assumed the reason such hook-ups were frowned upon were due to possible siphoning action.

   I am enclosing  an attachment of a page from Charlie Wing's The Visual Handbook of Building and Remodeling which depicts these various trap correlations.

   As for Jelio's situation being 2 seperate sinks...thank you for interjecting and correcting me...I thought Jelio was talking about connecting up a double-bowl, single vanity...which is the exact set-up I have in my own bathroom.

   I believe my advice given based on my assumption of a  single vanity having a double-bowl sink was correct. However, since that was not the correct assumption on my part, thank you for correctly diagnosing the situation and posting your response.

   Davo

   
1. 
   Wet_Head | May 19, 2003 09:01am | #14

   like I said... nothing personal... but I am going to research the double bowl issue...  I will let you know what I find OK?

2. 
   Davo304 | May 19, 2003 09:20am | #15

   Sounds Ok to me.

   One more question. Jelio said that his/her sink configuration was to be 2 sinks, mounted 30 inches apart, housed in one vanity top. Is there something in your particular  Uniform Plumbing Codes book that says sinks mounted 30 inches apart must have seperate P-traps? As you can see from the drawing I attached (kinda small and hard to read I know) this particular book is saying that up to 3 sinks can all be hooked up to a single P-trap, so long as each waste arm of the sink is no more than 30 inches away from the trap. According to this explanantion, Jelio could have hooked up to one P-trap only and been legit.  Perhaps this is no longer acceptable?

    Hope you can shed some light on these issues.

   Thanks.

   Davo

3. 
   Wet_Head | Jun 04, 2003 11:22am | #16

   the 3 sinks you mention is a 3 compartment sink.  it is one unit.  the lavs are 2 units.  a kitchen sink is 1 unit.  unit = fixture in this case

4. 
   Erich | Jun 04, 2003 04:16pm | #18

   Hey WHW,

        I was thinking about tackleing this same project but due to time constraints, learning curve, etc..., I'm having my very qualified and friendly neighborhood plumber rough this one in for me.  So my question is really just to ensure that he's doing it the way it should be done and for my and everybody's own info.  For some reason, the correct plumbing for this set up is difficult to find, even in Peter Hemp's book which I read after so many rec's from peope here (great book none-the-less).

        SO, what would your perferred method be for doing TWO sinks set in one top, 30"o.c., etc..., NOT a single unit double sink?  Each drain gets it's own P-trap, then back to the wall and individually san-t'd?  Then how to you get the farther of the two branches into the other, a combo maybe?  This is probabaly all wrong, maybe it would work, but I'm sure you have a more elegant approach. 

        Thanks for the help and insight as usual!

                                             Erich

5. 
   Wet_Head | Jun 04, 2003 06:39pm | #19

   dual outlet san tee.  then use 90's to come out of the wall.  offset your stubout 2" from center of the sink.  makes it easier to install p-trap.

6. 
   NormKerr | Jun 04, 2003 07:23pm | #21

   For two separate sinks sharing one countertop:

   it sounds like, if you have the opportunity to re-do the in-wall plumbing (or are doing it now for the first time), running two separate traps to the stack is best.

   but if you have only one outlet from your stack (adding a second sink during a remodel, say) I've always seen both sinks feeding one trap (to avoid siphoning concern).

   One thing I always liked about a shared trap is:

   if you don't use both sinks all the time, one trap could dry out.

   but if you share the trap it'll always stay "wet".

   Not a plummer, the above comments are intended to confirm if my thinking is ok or not, from you plumbers listening.

   Norm

7. 
   Wet_Head | Jun 04, 2003 07:46pm | #22

   doesn't meet code for starters.  good question though and shows you care about it being done right.

8. 
   nino | Jun 04, 2003 09:30pm | #23

   I was always told,

   2 separate fixtures, 2 separate traps both with their own back vent.

   The only time a shared trap was allowed was if you're doing the drain on a single fixture, multiple sink.

9. 
   HeavyDuty | Jun 04, 2003 09:44pm | #24

   WHW, a little twist here for a related situation. For a double kitchen sink, can you P-trap them individually and drain into the same arm? The instruction on the kitchen pig suggested that's preferred.

   Tom

10. 
    VtMike | Jun 06, 2003 02:21am | #27

    Right, seperate trap for each fixture. A two bowl sink is one fixture. Two lavs on the same countertop are two fixtures. Maximum vertical distance to trap weir is two feet. Traps must have an easy means of cleaning. Means no gluing everything together.

    Exceptions:  One trap is permitted on combination fixtures as long as one is not more than 6" deeper that the other and waste outlets are no more than 30" apart. Also one trap is permitted for a set of not more than three single compartment sinks, laundry trays or lavs adjacent to each other in the same room and with the trap centrally located.

    When in doubt, check the book - BOCA Artical 10 Section P-1001.0 Fixture Traps

    FWIW, I prefer one trap per fixture. Lav drains tend to get stinky if they are too far from the trap.

11. 
    Erich | Jun 05, 2003 07:37pm | #25

    WHW,

         Thanks for the tip.  I really don't want my plumber to set up a wet vent situation, and it seems that even amongst professional plumbers there are many variations, some of them not good ones.  I assume with your set up the double san-tee is BETWEEN the two sinks behind the wall?  That only makes sense.  I'll be roughing in the wall for him, so I could provide some extra room there for him to work in (I'll tell him he owes you!). 

         Re Hemp's book, I liked it because of the detail, though I'm looking at it from the standpoint of a guy who's doing mostly learning, not mostly DOing.  I can see if you were the later that you might omit a lot of what he does, especially if you're really experienced.  Well, thanks again!     

12. 
    Wet_Head | Jun 05, 2003 07:40pm | #26

    I assume with your set up the double san-tee is BETWEEN the two sinks behind the wall?  That only makes sense.

    you got it.  good luck

13. 
    Wet_Head | Jun 04, 2003 06:42pm | #20

    btw, I never cared for Hemp's stuff.  personal opinion I guess.  too many tips that made the job more complicated instead of the other way around.  he just has a different mentality than I do.  but some like it and that is good.

3. 
   JerryAlbrech | Jun 04, 2003 03:51pm | #17

   I have a similar vanity and attached is a picture of what I did to avoid a wet vent as they call it.