Fill a clean, clear bottle—like an old soda bottle—halfway with tap water. Add three drops of liquid dish soap (the cheap, non-dishwasher kind). Shake it like you’re mixing a martini, really aggressively, for ten seconds.
Look at the suds. If you see a thick, fluffy layer of foam that sticks around for a solid minute? Congrats—your softener is working, and you’re living in luxury. If you get a thin, sad layer or no foam at all, and you notice cloudy water? Then your softener is kaput or the salt is gone. (Side note: this test works because hard water minerals kill soap’s ability to foam. The more suds, the softer the water—it’s math, but the fun kind.)
