A lavatory p trap i assume is a toilet. This depends on whether the toilet is wall hung, cemented down or screwed down. Low level or close coupled?
$800
Infinite. It doesn't affect it at all. Vertical distance doesn't have an affect on a trap.
Yes. It prevents sewer gases from entering by way of the water trapped at the elbow. Gases need an upflow which is eliminated by the P-Trap. It's not a pee trap, it's a p-trap. Yes you do need a...
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