Poll -- increasing trap arm diameter?

[Reach4]

Dang. Stupid miss-type in the poll title. I meant 2.9 ft. Wish I could edit that.

In the sketch, assume that this is under a north-facing window.
A 1-1/2 inch slip joint trap feeds into a trap adapter. That continues into a 2 inch bend, 2 inch pipe, and 2 inch santee. Assume total developed length from U bend to santee is 2.9 ft. That was selected to be under the 3 ft 1.5 inch trap arm max for UPC.

Comments on aspects would be good too, such as if a 90 degree bend for horizontal to horizontal can be a medium bend, or must be long sweep, under some code.


Poll answers can be changed. More than one choice can be selected.

The

 

[hj]

You can do anything you want to, (except make the trap arm less than 1 1/2"), but it would be ridiculous to do so.

 

[Sponsor]

 

[Terry]

I have done both 1.5" and 2" trap arms for kitchens.
The 2" was so that I could have a full size cleanout.

 

[Reach4]

I was basing this poll on things like https://terrylove.com/forums/index.php?threads/reducing-2-to-1-1-2-kitchen-pipe.88393/#post-634003

 

[Tuttles Revenge]

Besides the typo.. I don't quite understand the purpose of the poll.

A 1.5" trap arm has a limit of 42" while a 2" trap arm would be limited to 60"

The notion that the same sized trap needs to be feeding the trap arm is probably some outdated non engineered notion that a group of cigar smoking old guys made up and patted each other on the backs cuz they got paid by the letter. How many 1.25 trap arms are installed today to a lavatory with an 1.25" trap.. none.

We install medium sweep ells for the trap arm termination to the trap all the time. I had One inspector tell me it needed to be a long sweep but that it was OK this time.. thousands of inspections and installations later its never come up again.

 

[Reach4]

Besides the typo.. I don't quite understand the purpose of the poll.

See https://terrylove.com/forums/index.php?threads/reducing-2-to-1-1-2-kitchen-pipe.88393/#post-634003
wwhitney generally does a good job at interesting codes, so it seemed that the increase in trap arm diameter may be forbidden by UPC 1003.3. I wanted an opinion of how people interpret the rules.