S trap or strange P trap?

The trap arm doesn’t go straight down like a typical S trap that I see. The pipes certainly make an S shape though. Appears the trap would not siphon out but figured I would ask the plumbers out there. Call it out?

Under certain conditions, yes it can siphon dry, and is definitely wrong. It appears like a poorly executed vertical leg trap (only allowed in few areas). No need to call it an s-trap, it is configured incorrectly for several reasons. Just let the plumber correct it :slight_smile:

Thanks Simon

As Simon said …improperly-configured trap.

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Thanks Kenton, Thanks Jeffrey

Leaking above the trap.
Inappropriately configured plumbing trap.
Chance of siphonage.

In plumbing, a trap is a device which has a defined shape by utilizing curves or/and angles along a pipe path, to abduct gray or waste water, and prevent backflow or gases, vermin or insects from entering a building, while allowing any gray or waste water to continue flow downstream.
Just below a Sink or Wash Basin is the Tail Piece. An Inlet drain pipe mounted just above the Trap Adaptor connected to the Plumbing Trap.

The Plumbing Trap below the Trap Adapter in this image is referred to as a P-Trap, which in of itself, is a Plumbing Fixture and device.
plumbing trap

P-trap consists of the Inlet, Trap Adapter, Top & Lower Dip, P-Trap, Cleanout, Trap Weir Seal or Crown Weir Seal below the Trap Crown, Outlet and Trap Arm.

A Plumbing Trap, by definition, is a device that retains a measured amount of water. When, in this case, lavatory fixtures are utilized, an amount of water is retained in the P-Trap while the rest of the water is drained. The water that remains in the P-Trap device is referred to as, The Trap Seal.

P Trap serves several functions.
1: Backflow prevention.
2: Trap Debris.
The Trap Seal serves several functions.
1: Prevent Sewage Odors & Gases, a complex mixture of toxic and nontoxic gases produced and collected in sewage systems, from escaping/dispersing into the room.
2: Impeding Vermin, Mice and Insects from exiting the drain pipe into your home.

The above image or a P-Trap was provided by InterNACHI, International Association of Certified Home Inspectors. The world’s largest inspection trade association founded by Nick Gromicko.

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Doesn’t matter if it goes down 3” or 3’. A vertical drop of any length from the p trap now makes it a s trap. Others will argue but show me the code. In a code book it’s either a p trap or an s trap. Of course there are other variations such as a drum trap. No such thing as an incorrectly installed p trap when it is clearly an s trap.

Years ago in plumbing school there was an example of a wye with the branch end turned up to revive an elbow. Most would consider this a horizontal to horizontal transition. But wait, there was a 3” piece of pipe connecting the elbow to the wye. It was a small butt piece much like your photograph. Now it’s a horizontal to vertical to horizontal transition. Now the elbow can be made short sweep instead of long sweep. Fitting directions in flow make a difference. It doesn’t matter if it’s a butt piece or a 3’ section or pipe as rules are rules. Maybe it was an incorrectly installed horizontal to horizontal wye LOL.

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Thanks Robert and Martin.

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