TRAP ARMS

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Asktom

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My newest UPC code book (2000) states in 1001.1 that "Not more than one (1) trap shall be permitted on a trap arm". Yet I see persons whose opinions I respect on this site referring to two traps on an arm for kitchen sinks, often using a double wye with a CO on the third inlet. Is my code book out of date or is this just a specification that most ignore?
 

hj

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WE ignore it. In fact, I have seen "commercial three compartment" sinks with three traps on the arm. And in my previous house, I had separate traps for all three sink basins.

dwv_traps.jpg
 
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Asktom

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HJ, that is the impression I got, interesting. Where I worked in Southern California I rarely saw two traps on an arm and the inspectors certainly wouldn't pass it - people have told me they got turned down for putting a cleanout on the trap arm because somebody MIGHT use it to add a second trap. I'll have to admit, given my plumbing upbringing, that I can't understand why plumbers on this site who would gasp in horror (hey, it is Halloween) at two showers on one arm have no problem with multiple traps on an arm for sinks. It is curious the parts of the code that get brushed aside in different areas.
 

FullySprinklered

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In my area, I often see three traps under the kitchen sink. One for the d/w, one for the disposer, and one for the other sink bowl. They're usually glue up, and when the new granite and sink go in, I have to sawsall the whole mess and go back with an end-outlet waste and cap off the unnecessary nubs. Run the d/w into the disposer.

And, after all's said and done, the kitchen sink is still just one fixture no matter how many traps are crammed under there. Way overkill in my humble opinion, to put all those glue-up traps under a kitchen sink, unless there's some burning reason to do so.
 

hj

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two traps on one sink is one thing because it would be difficult, or at least unusual, to use both at the same time, whereas, it would be easy for two people to be using the showers at the same time. Since I NEVER use "glue up traps" anywhere, when I do two or three traps under a sink, they are all tubular.
 

Asktom

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HJ, I guess I have to respectfully disagree with you on this one. The code is as the code is enforced so multiple traps on sinks my fly in your area, but it clearly not in conformity with the UPC. It wouldn't pass where I worked, but I was really just curious.
 
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