pH is a measure of how acidic or basic your water is, but the actual pH of water changes as its temperature changes. This means a water sample taken from a cold plunge and tested at a pool store, after the water has warmed up to room temperature, can show a noticeably different pH reading than what the Crystal Water Monitor displays.
pH20 is your water's pH adjusted to 20°C (68°F), which is a standard reference temperature used by most pool stores and test equipment. By normalizing to that same temperature, this reading gives you an apples-to-apples comparison when checking your results against an outside test.
When should I use this reading?
For most pool and spa owners, the standard pH reading shown in the app is the right one to use for day-to-day water management. However, if you have a cold plunge or cold water feature, use the pH (Temp Compensated) reading when:
- Comparing your results to a test strip or liquid test kit
- Cross-checking with readings from a pool store water test
- Discussing your water chemistry with a pool professional
Why do the numbers differ?
When you pull a sample from cold water and bring it indoors or to a pool store, the water warms up — and as it does, the pH shifts. Neither reading is wrong; they're just measuring the same water at different temperatures. The temp compensated value accounts for this, so you're comparing the same baseline.