Mid way P-trap

[Denray]

Any reason for a P-trap, minus a vent, mid way down a long drain run? No sink upstream, just a clean out. Good luck with that.

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[kurt]

Looks like a house/building trap. What diameter is the pipe? Is it the main sewer out of the building?

[Denray]

Seems like it was 3 inch. It goes about 8 feet back behind me to the exterior wall. It travels down to a much larger drain.

[kurt]

If it drains to the exterior wall (can't tell from the pic which way it's pitched), it's probably an old building trap. We don't have them around here, don't know what California does with them.

[Denray]

It's draining away from me towards middle of house. Weird.

[kurt]

Where's the sewer exit? Is it in the middle of the house? Could be, if it is, I'm sticking with building trap. Just a WAG....

[John Kogel]

If it's unusual, it is usually wrong. There's no easy way to clean the rust and sludge out of it.

[Denray]

Yep, I've seen vents way far away from a shower P-trap, or not at all, but never a P-trap out in the middle of nowhere with no fixture above it. Well, maybe one other time.

[Jim Katen]

It didn't always do nothing. Something changed.

[Jim Baird]

...I once inspected a group home under construction where the plumber had installed a "master trap" with two cleanouts before and after trap. It is related to commercial rqmnt for grease traps and separation of soil drain from kitchen drain. Technically I think it was not necessary in what is called a "six-pack" (six or fewer in group home setting where manager is POA for old folks w/o family or insurance). In the current setting it was overkill.