When you enter water reports in the app you might notice that the app shows a range instead of an exact number. Crystal automatically creates a range for your water report measurements based on the testing method you selected or used when you created the water report.
No Testing Method is Perfect
Every kind of pool or spa water test, like test strips, liquid drop kits, electronic tests, or SpinLab tests, give results that are close, but not always exact. Things like water temperature, lighting, the age of the test strip or drip chemicals, or how long you wait to read the colors can change the values of your test.
Test Strips Have the Widest Ranges
Test strips have pads that have been soaked in special chemicals that change color in the presence of a specific water condition. These chemicals have a limited range of output colors and are not always a smooth gradient between colors. This means that the pads "snap" to the closest color in it's limited set based on your water. In addition to the pad chemistry, test strips can be affected by:
- Waiting Too Long - the pads continue to change colors as they sit. It's important to take your color reading after a few seconds but before 20 seconds since dipping.
- Lighting - It's harder to discern the colors in poor lighting.
- Age - The pad chemistry isn't as reactive in older test strips.
- Interpretation - Everyone has a different interpretation of colors and how they match the bottle chart.
Because of all of this, a pad that says “looks like 2 ppm” might really be anywhere between 1.5 and 2.5 ppm.
How We Help
Our app knows that test strips, drops, and SpinLab tests all have different accuracy levels. So when you tell us the type of test you used, we automatically:
- Use its resolution (the smallest increment it can show).
- Add a range that matches its real-world accuracy.
That way, your results make sense to the chemistry math behind your pool — and you see what’s actually happening.
Your pool doesn’t care about the last decimal — it just wants to stay balanced and happy.