Grab a clear, empty water bottle—the one from your last road trip works fine. Fill it about halfway with tap water, then add three drops of pure liquid soap. (Not dish soap, not detergent—just plain soap, like Castile.)
Now, put the cap on and shake it like it owes you money. Seriously, give it a good ten seconds. If the water turns cloudy with a sad, thin layer of suds on top, you’ve got hard water. Soft water, on the other hand, gives you a mountain of fluffy foam that looks like a bubble bath for elves.
Don’t trust the foam? Look for scum. Hard water leaves a ring of white, greasy residue around the bottle neck. That’s calcium reacting with the soap. (Nature’s way of saying, “Your water is stubborn.”)
The "Spot Check" Method (It’s Literally Just Checking Spots)
Next time you wash a glass, let it air dry—no towel. If you see white spots or streaks where the water droplets evaporated, that’s hard water’s calling card. It’s literally leftover minerals, like tiny salt flats on your favorite mug.
If those spots are hard to scratch off with your fingernail, you’re in the very hard zone. I once had a glass that looked like it had a permanent case of dandruff. (Not a good look for your wine night.)
How to Filter Water in Your Country House or Cottage – A Complete Guide
