newbie trap question

Specific Inspection Topics Plumbing Inspections
1

I’m a tad confused about the washer stand pipe standard:

18"-42" above the crown weir, but 30" above the trap weir?

I don’t get the implied difference. What am I missing here?

Thanks,
Tim

2

I get 34 inches.

Washer drain needs to go up so there is no siphon effect.

3

Hmm. Not sure how to interpret that.
Where does 34" come from?

Tim

4

The 18" to 42" rule is from IPC.

The 30" rule is in the IRC.

Somehow, in whatever you referenced, they appear to have been combined.

5

Thanks, Jim. Now it makes sense.

Cheers,
Tim