vent connection above or below u trap?

Answer 1

the air in the pipe has to have somewhere to go and is usually placed before the trap to allow air to escape or to draw air into the pipe behind the water to allow it to drain like something was pushing it

Answer 2

The u trap doesn't need to be vented it is the stack pipe where the pipe with the u trap discharge that need to be vented.
For the u trap to function the water in it needs air pressure on both sides of the u trap.
In a toiled the water has air pressure on the top,without air pressure from the other side,the water would flush down and eliminate the trap.

Answer 3

you have the fixture(the sink or whatever) and from that drains into the p-trap and then usally within 36 inches you will have the vent branch. there is proper sizing depending on the size of the pipe(1 1/2" or 2"), up to 5 feet away depending on the code book.

if it is a shower, try and have the vent branch, or wye, also tilted up to a 45 degree to prevent water from going in to the vent line. and have it within about 5 feet or closer the better.

so the fixture is upstream, the p-trap next, and then the vent branch downstream.

Answer 4

Drain pipe (main) will connect to the left side of U-Trap horizontal and other side which is vertical to the sink or any kind of features .Now VENT pipe must install in continue main drain pipe to the roof and is above any plumbing system ,this vent prevent pressure differential to keep the odor down to the drain system .

Answer 5

Above. Otherwise it could get "waterlogged" and defeat the purpose. Vents are to allow air to the drainage system.

Answer 6

Above, otherwise it will vapor lock.