OK, I understand that P traps is OK and S trap should be avoided, codes, etc.
I understand how an S trap can be siphoned and it will be empty. why that does not happen with a P trap as well? if there is enough pressure difference, can't a P-trap be siphoned?
second question: I did some work recently and I noticed that the connection between P trap and trap arm does not have a seal. Why? they give you a washer to put between drain and P trap, but no washer between P trap and arm.
Thanks
EDIT: example here, they show slip washers between tail pipe and P trap and between Arm and wall, but not between P trap and Arm
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Edited 1 time(s). Last edit at 08/16/2020 10:04PM by space-time.