My house, built 1950, was owned for a long time by a gentleman who performed puzzling and/or illegal repairs and modifications. One such modification is shown below.
A branch of copper 3/4" pipe comes off the main drain line just before it goes below the basement floor (after which the main drain pipe runs 6' towards the camera and picks up the utility sink drain before exiting the house to camera left), and goes into the wall below the crawlspace to points unknown. The floor of the crawlspace is just a couple of inches below the sill visible in the first picture, and the wall itself is a structural cinder block wall.
You may notice that it appears to be designed to keep water from flowing into the drain from wherever that pipe ends up.
All drains in the house are accounted for, and that isn't one of them. All downspouts empty onto the ground; there is no downspout-related piping anywhere at the exterior.
Two plumbers have looked at it and been unable to say more than "whatever it is, it doesn't look legal," and "if it ain't broke, don't fix it."
The trouble is that I think it may be related to an odor problem we're having in that area. A crawlspace guy said "that's sewer gas, you need to call a plumber," and the aforementioned plumbers say it's not sewer gas.
The second plumber localized the smell as emanating from two of the cinder block openings near the pipe, but looking down those with a flashlight reveals no dead animal and a totally dry condition. Plugging the cinder blocks with plastic bags eliminates the odor entirely, but we are concerned with what the odor might be signifying that we should be fixing.
This has apparently been an ongoing problem, as the previous homeowner threw baking soda (which our home inspector mistook for efflorescence) all over the stone foundation in the crawlspace.
a) Any idea what that pipe might be for? (My best guess is some sort of poor man's gravity-driven sump pump or a sewer overflow diverter that empties into the foundation - but for the love of god why?)
b) Could it be related to the odor problem, and if so, what would be an appropriate course of action?