Tub drain p trap problems

[Jdoerfler93]

All,

I have an antique claw foot tub I'm installing. The drain is a brass 1.5" pipe going into the crawlspace. This is replacing a shower that used to be in the same location. When I went under to see the previous setup I got puzzled. The old shower drained through a 1.5" pvc pipe into a 2" trap that went under and around a floor joist, then came out of the trap at 1.5" again. I know code doesn't like reducing drain sizes. Is this technically allowed because the entry and exit from the trap is 1.5", or is this against code? The only reason I'm wondering is because tapping into existing is always more fun than running new.

Thanks in advance!
Joel

 

[GrumpyPlumber]

Pics would help.

That said, it shouldn't decrease downstream, increase is fine, the real question is "under and around a floor joist,", I'll guess the trap dip loops under the joist...

 

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[Jeff H Young]

I'm not sure what you got going but I'm sure its bootleg poor work but we all know water will drain through just about anything for a while . We sure can't imagine a new sew piping plan on your info though