Testing - Grotek pH Test Strips Kit Narrow Range pH Test Paper, also known as litmus paper, will help you determine your pH measurement without a pH pen. Grotek pH Papers measure pH ranges from 5.5 to 8.0 The "Narrow Range" from 5.5 to 8.0 means that you're given a much more exact indication of your water's pH (instead of having to judge along a much wider color scale range) - this is a very inexpensive and awesome way of testing the pH of your water!