Okay, here’s where people mess up: they just fill a cup from the tap and hope for the best. Don’t do that. Arsenic can cling to pipes or settle in sediment, so you need to flush the system first. Run the cold water for two to five minutes before collecting—this pulls fresh water from the well, not what’s been sitting in your plumbing all night.
Use a clean container (the lab provides one, or use a glass jar you’ve boiled). Fill it to the line, cap it tight, and label it with the date, time, and location. Yes, treat it like a crime scene—you’re the detective. Ship it overnight if the lab says so; some contaminants degrade fast.
