I need to know what is the difference between a P-trap which has a U shape with a horizontal pipe and the bottle trap which consists of a horizontal & a vertical tube with a removable cup at the bottom. What's the use of each one?

A "P" trap,(see image) is a device that maintains a 3" deep layer of water in the pipe to serve as a seal to prevent sewer gasses from coming up the drain into the structure. The codes require all fixtures to be equipped with a trap, but in the case of a bathroom lavatory either a P-trap or a Bottle Trap,(see image) can be used interchangeably, depending upon what you desire.
A common trap uses an inverted U shape section to hold the water. A barrel trap or bottle trap is a round container with a standpipe up the center similar to the standpipe in the toilet tank. The drain water enters the trap near the bottom of the Bottle, as it enters the outer chamber the level in the chamber rises and it then spills over the inner standpipe and on down the drain line.
Bottle traps are used where the trap's exposed and a decorative trap is desired. Is this what you wanted to know? Regards, Tom

Dear Tom

Thank you so much for your reply. Now I got a full image about this issue. So, a bottle trap cannot afford the advantage of keeping the sewer gases from coming back into the drainage system, right?

Also I need to know what does it mean an anti-syphon trap .

Thank you so much

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Originally Posted by maccad

Dear Tom

Thank you so much for your reply. Now I got a full image about this issue. So, a bottle trap cannot afford the advantage of keeping the sewer gases from coming back into the drainage system, right?

Also I need to know what does it mean an anti-syphon trap .

Thank you so much

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Both bottle and "P" traps will prvent sewer gas from escaping. While a "S" trap, being a unvented trap, will allow the trap seal to be siphoned off, Bottle and "P" traps being vented will not. Hence, "anti-syphon trap".
Happy thanksgiving day, Tom

Dear Tom

Happy thanksgiving to you too my friend.

Now I understand the term antisyphon so well. But what still confuses me is how a bottle trap keeps the gases from flowing back. The water remains at the bottom of thet cup part, so gases can freely come back from drainage into the system.

And what do you mean by vented? How are the bottle and P-trap vented? Do you mean the air vent that exist in the drainage system?

Best Regards

"But what still confuses me is how a bottle trap keeps the gases from flowing back."
Let me try to explain it better and this time I'll attempt to keep it simple. The discharge enters the bottle trap through a stand pipe that reaches under the weir, (bottom) of the pipe going into the wall. The bottle fills up and drains into the wall pipe. When the discharge stops the liquid left in the bottle stays there until the fixture's drained again. The stand pipe that extends below the liquid left in the bottle prevents any sewer gas from entering the lavatory and the trap's sealed.

"And what do you mean by vented? how are the bottle and P-trap vented? Do you mean the air vent that exist in the drainage system?"

The pipe in the wall drains into a drainage tee. The bottom half of the tee directs the flow downward into the sewer main while the top part connects to a pipe that runs up through the roof and vents the system. Did that clear things up a bit? Happy Turkey day, Tom

Thank you so much for your help. I got it all now :)