You can establish whether your water is hard in about ten minutes without buying anything, because hardness announces itself in ways that are easy to check once you know what to look at. Getting the exact figure needs a test, but knowing whether you have a problem worth measuring does not.
The four signs to look for
Pull the aerator off the kitchen tap and look at it: a chalky white deposit is hardness, and how much has accumulated tells you how quickly it builds. Look inside the kettle for the same white crust. Check the shower screen and the taps for a film that returns within days of cleaning. And notice how the soap behaves, since hard water produces poor lather, leaves a scum ring in the bath and leaves skin feeling tight after washing. Two or more of those together is a confident answer.
The soap shake test
This one costs nothing and is a genuinely useful indicator. Part fill a clear bottle with cold tap water, add a few drops of pure liquid soap rather than detergent, cap it and shake hard. Soft water produces a generous head of lather that persists, with the water below staying clear. Hard water produces very little lather that collapses quickly, and the water below turns cloudy or milky with soap scum. The more soap it takes to get a lasting lather, the harder the water is.
Getting the number
The USGS classes water as soft at 0 to 60 mg/L as calcium carbonate, moderately hard at 61 to 120, hard at 121 to 180 and very hard above 180 mg/L, and knowing which band you are in is what decides whether treatment pays and what capacity it needs. On a municipal supply the annual Consumer Confidence Report often carries the figure, which makes it free. Otherwise a titration kit or test strips give it in minutes. Softener settings are usually entered in grains per gallon, so expect a conversion.
What not to use
A TDS pen is the wrong instrument, and it is the one most often bought for this. It measures conductivity from every dissolved ion, so sodium, chloride and sulfate all count towards the reading alongside calcium and magnesium, and two supplies with identical readings can differ completely in hardness. Worse, softened water reads about the same as it did untreated, because sodium replaced the calcium ion for ion, which regularly convinces owners a working softener has failed. Our hardness testing guide covers where to send a sample.
Questions people ask about how do i know if my water is hard
What is the quickest sign of hard water?
A chalky white deposit on the kitchen tap aerator and inside the kettle, plus a film on the shower screen that returns within days.
How does the soap shake test work?
Shake cold tap water with a few drops of pure liquid soap. Little lather and cloudy water below means hard, a persisting head means soft.
Where can I get my hardness figure for free?
The annual Consumer Confidence Report on a municipal supply often carries it. Otherwise a titration kit or strips give it in minutes.
Can I use a TDS meter for this?
No. It measures all dissolved ions, not just calcium and magnesium, and softened water reads much the same as it did untreated.