A sometimes-customer called me about a leak. I get there and there's water in the main heating duct that runs through his basement. I look all around, follow all those CPVC pipes (some other plumber installed years ago) that are lying on the duct, and crawled back into the crawl space. Coluldn't find a leak.
I go to the truck and cry for a few minutes, then it occurs to me that the drain pipe from the toilet is partially boxed in a make-shift duct that connects to the main duct. Yeah, it looks as strange as it sounds..
I have the customer flush the toilet, while I monitor it from the crawlspace. Sure enough, I hear the toilet water flowing down the heat duct!
I run upstairs and get the low down on the new toilet. Seems that he bought a terrible Kohler toilet from Lowes and had the Lowes sub-contractor install it. Well, the Lowes installer anchored the toilet with wood screws---instead of closet bolts---and used a skinny wax ring. Hacks, the lot of 'em.
Well, that's not the whole problem. As I'm flushing the toilet and laughing at Lowes and my customer for hiring Lowes, the toilet backs up into the tub! A mainline sewer stoppage, too!
This sewer has been a headache for every plumber in town. Last year, I snaked it, jetted it, camera-ed it and tried to get him to replace at least the bad part, but noooooooo.......he said since I got it open, it'll keep.
Yeah, it kept, until it backed up a year later into a Lowes-installed Kohler toilet and sewage poured into his heat ducts!
Long story longer, I cleared the sewer stoppage with blades and a jetter, replaced the crappy Kohler-Lowes toilet, repaired the damage the Lowes installer did, and charged him accordingly.
Lesson learned: you may think you're saving money by cutting corners (going to Lowes and using cheap labor), but water is unforgiving. Don't cheap out on the plumbing.
A house without plumbing is a garage.