I didn’t realize this small cap outside my house is actually tied to my washer drain (the clean out) - and it could help clear a serious clog. Here’s how it works. Your washer empties into a pipe, which drops into a P-trap. That curve holds a little bit of water to block sewer gases, but it also collects lint, soap, and hair if your washers filter doesn’t already do it. Most modern high efficiency top loading washers don’t. Usually, I can clear a clog here with a drill-powered drain snake. Wiggl