This washing machine cleaner is septic-safe and works for both traditional and high-efficiency machines. 

Promising review: “This really works! Last year, our laundry started to stink after every wash, and no matter how much detergent, softener, or scented beads we added to it, there was still an unpleasant mildew undertone. Immediately since trying this, the funky smell is gone. This is part of our routine purchases now, and we do this at least once a month, sometimes two.” —Mbut

Price: $8.69