What is a p trap?

That is the trap under your sink and tub. It holds water to keep sewer gasses from coming into your home. Old chrome plated brass is prone to corrosion, almost all new ones are PVC. Not quite shaped like a "P " but that's what it is called. Why the question?

A Ptrap protects the health of all nations! A Ptrap is present at all plumbing fixtures in some manner... at sinks and tubs they are external, at floor drains and toilets they are internal traps, but all fixtures have a trap associated with them in some way.

The Ptrap holds water in the trap at all times so that sewer gasses cannot escape from the main/street sewer drains and enter your home. If water evaporates or leaks from the Ptrap sewer gasses enter the home and can make an awful smell and health hazard.

Years ago, they installed whole HOUSE PTRAPS and didn't install Ptraps at individual fixtures, but they soon found that sewer gasses were still an issue and did away with whole house traps and changed to individual fixture traps as presented!

Ptraps need to have a plumbing VENT associated with them to keep the traps from siphoning off the water when the fixture or another fixture associated with the bathroom group flow.

Mark

Love those images Mark.

Years ago, they installed whole HOUSE PTRAPS and didn't install Ptraps at individual fixtures, but they soon found that sewer gasses were still an issue and did away with whole house traps and changed to individual fixture traps as presented! Now you're getting into my area. I was around when we had houses that were roughed in with one 4" line running through the basement and out the roof. Each fixture had an "S" trap that connected in the basement. That was back in the 20's and 30's, To the best of my recollection we were installing "P" traps and vents in the 40's. Just a little bit of plumbing history for you. Cheers, Tom