Unless you have a microscope and a PhD in “gross stuff,” don’t try this at home. Send it to a certified laboratory—they’ll use something called a “presence-absence” test or a membrane filtration test. Basically, they let the bacteria throw a party on a petri dish, and if they show up, the lab calls you with bad news and a coupon for a water filter.
Surprising fact: most labs charge between $20 and $50 for a basic coliform test. That’s less than a decent pizza, and the pizza won’t tell you if you’re about to drink from a septic swamp. Some companies also sell DIY test strips or kits you can mail in—just don’t trust the ones that change color like a mood ring and call it science.
Clean Water: Understanding and Testing for Water Contaminants | H2O
