Grab a clean, clear plastic bottle with a tight lid—like an old soda bottle. Fill it about one-third full with tap water, then add a few drops of pure liquid soap (not detergent, just basic soap). Put the lid on and shake it like you’re mixing a cocktail for about ten seconds.
Now, look at what happens. If the water turns milky and cloudy and you see almost no suds, you’ve got hard water. If you get a nice, big pile of fluffy bubbles that stick around, you’ve got soft water. It’s not super precise, but it’s a fun, quick check—like a party trick for your kitchen sink.
