It definitely needs to slope away down to the drain. Specifically a quarter inch per foot. No more, no less. The reason for this is that at a quarter inch per foot waste water tends to sort of oscillate up one side and then the other of the pipe.

Which way does a drain trap go?

When you cement it together, the straighter side of the trap- which is not as curved- should be what the 90 degree piece is glued onto. Then the curved end should be connected to the shower drain. However, gluing the P-trap shouldn’t affect the drainage.

What happens if P-trap is backwards?

The outlet end of the trap pipe should be lower than the inlet when installed properly. The example shown has it backward, which creates a trap seal more than 4” and makes the drain more likely to clog—and that’s a long explanation for why a backwards trap is a bad thing.

How far should drain go into P-trap?

Maximum Distance

However, the Universal Plumbing Code stipulates that the total developed length of all tailpieces, arms and fittings connecting the drain to the p-trap must be 24 inches or less.

Does the P-trap need to be lower than the drain?

It is not ideal to have the p-trap below the the exit drain because water gravity has to force the water out instead of it flowing downwards naturally. They both work and have seen it many times. But essentially anything below already creates its own p-trap- so using another is redundant.

How should P-trap look?

Quote from the video:
Quote from Youtube video: If you notice a lot of extra piping under your sink then you're looking at the p-trap. Key traps are named after their shape.

How do you line a P-trap with a drain?

Quote from the video:
Quote from Youtube video: So you have to cut that distance such that when you slide the p-trap up against it it will be there and perfectly level to go straight into the center of that pipe.

Do P traps prevent backflow?

The P-trap functions by establishing a natural water seal. Water can flow into the overflow pipe, but not back into the sink. The water seal in the bottom of the trap prevents backflow. This prevents sewer gas from entering the trap.

Can a trap arm have an elbow?

A trap arm can have bends in it. I posted about this in previous threads. Yes there are limits as to the total number of bends. Yes there are limits as to the total length of the trap arm.

What is a trap weir?

The trap weir is the point at the bottom of the trap arm pipe where it connects to the trap. It’s the height at which water will no longer flow from the trap via gravity—the rim of the cup, so to speak (see “How Siphons Are Created,” below).

Does plumbing vent go before or after trap?

The simple answer is if your trap from the fixture cannot see the vent then it is installed wrong. We must always keep the vent connection above the trap weir to prevent siphoning and keep proper pressures on both side of the trap.

How are drains vented?

A plumbing vent pipe works alongside your drain pipes, except it doesn’t carry water. Instead, it regulates the air in your plumbing system. Also called a vent stack or plumbing air vent, the vent pipe regulates airflow to assure waste and water flows through pipes that drain out of your house.