Premium Water Hardness Test Kit | Fast and Accurate Hard Water Quality Testing Strips for Water Softener Dishwasher Well Spa Pool, etc. | 0-425 ppm | Calcium and Magnesium Total Hardness (150 Strips)

Very imprecise. Colors change and fade, and even if you manage to do it right, you end up with a wide scale between two colors and you have to estimate with a LOT of error margin. Buy an electronic tool instead, don’t waste your money on this.

Was hoping for it to work but it turned my tap water, the blu ionic filter water and my building pool water all the same colour of light brown. Would have excused the blu ionic filter and tap water being same but the pool water was also the same light brown. So far not impressed with this and initial impression is that its a waste of money for me but i'll see if i can test it on some distilled water later, not that it will be of any help to me because i wanted to test if there is any difference in colour between blu ionic shower filter and tap water.