02/17/2024
Look, it's my old nemesis S-trap! These kind of traps (the part of the white pipe that looks like a backwards S) have been illegal for at least 80 years (I can't find a specific date), but they're still everywhere, especially in older homes.
Traps are used to prevent sewer gasses from entering the home. They do this by "trapping" some waste water in that bottom "u" section. The water acts as a seal. The problem with s-traps is their design doesn't do a great job with this. They're prone to syphoning the water out, which leaves the trap dry and ready and waiting to let those lovely gasses into your bathroom or kitchen. Not all s-traps have issues with this, but enough do for them to be banned by plumbing codes. There are also issues with venting, but I don't think you want me to write a novel for ya, so I'll stop there.
Anyways s-traps are everywhere, but what I don't see all the time is what's going on with the grey hose in the picture. That's the drain line from the dishwasher. See how it enters the main kitchen drain below the trap? Yeah, that's how you get sewer gasses in your dishwasher.
Have a good day!
