YES, you do need a trap. Usually the bathtub drain is on the same sewer line as the nearby toilet.The smell from the toilet's discharge will sneak up through the bathtub's drain line without a trap ... not pleasant!.
a tub drain has an over flow and a waste drain that tye together at the tub then it is usually connected with a compession joint to an 1 1/2" trap that goes to a san-tee that should not be more than 5' away.
A typical p-trap in a sink or bathtub holds around 2 ounces of water.
The bathtub trap for a tub located directly on a slab foundation is in the soil under the concrete slab. The builder should have left a small opening in the foundation around drain and trap so that it may be serviced in the future. WIth some excavation you should find the trap about eight inches below the slab surface probably in the direction of a wall where the drain vent stack will rise up through the foundation as well.
To properly install a p-trap assembly in a sink, follow these steps: Remove the existing p-trap assembly, if applicable. Place the new p-trap under the sink drain. Connect the trap arm to the sink drain and the trap bend to the trap arm. Tighten the slip nuts with pliers to secure the connections. Check for leaks by running water through the sink. Make adjustments if needed to ensure a proper seal. Test the sink again to confirm the p-trap is installed correctly.
When you flush the toilet, it can create a vacuum in the plumbing system, causing air to be pulled through the drain. This air can pass through the water in the bathtub trap, creating a gurgling sound.
To properly install a p-trap assembly in your plumbing system, follow these steps: Cut the pipe to the correct length. Attach the p-trap to the drain pipe. Connect the trap arm to the drain pipe. Secure all connections with slip nuts and washers. Test for leaks by running water through the system.
The difference between a gully trap drain and a floor drain is placement. A floor drain is in a floor, a gully trap drain goes on an external wall.
Increase from 1 1/4 inch drain to 1 1/2 inch drain,,,,,, Lower the 'P' trap.,,,,,,,,,,, I did this with my Bathtub, It will go from completely full to empty in less than A minute.
Washing machines pump out a large volume of water and todays standards require a 2 inch drain pipe. Bathtubs generally have a one and one half inch drain. So bathtub drain will have to be increased to 2", including trap and 18 to 24" standpipe to operate correctly, and connected to the closest existing 2" line or larger line. Same 11/2 venting can be used.
Trap seal loss occurs when you have poor venting and as one fixture drains it creates negative pressure created and it pulls the trap seal (water) from another trap and allows sewer gases to enter the structure
An S trap would go through the floor. A P trap goes through the wall. As long as the drain is below the bottom of the sink, it should drain. Distance between the bottom of the sink, the trap and the drain does not matter, it just changes how much water stay in the drain. Normally it is just in the trap, but it can be above the trap if circumstances cause the trap to be lower than usual.