Here’s a little secret: TDS is closely related to electrical conductivity. Clean water doesn’t conduct electricity well, but water with dissolved solids does—like adding salt to a science fair battery. You can buy a cheap conductivity pen that also gives you TDS readings. Or, if you’re really lazy, there are smartphone apps that claim to measure TDS using your phone’s camera flash and microphone.
Spoiler: Those apps are about as accurate as a blindfolded dart thrower. They’re fun for a laugh, but don’t rely on them for your fish tank or your expensive espresso machine. Still, if you want to pretend you’re a water wizard, download one and wave your phone over a puddle. “Your TDS is 762 ppm!” you can announce dramatically. Nobody will fact-check you.
