If you're referring to a sinks P-Trap, ... all sinks require them. Now, some of the P-Traps I've seen do have the threaded clean-out cap (on bottom of trap). Whether their required or not is unknown to me. If they have the clean-out cap, .. great, ... if they don't, it's just a matter of uncoupling the P-Trap, removing it and cleaning out all of the gunk and wifes hair !!
