If you’re under an industrial stormwater permit, chances are you have had to analyze the pH levels of your stormwater samples. Currently, the hold time for pH is 15 minutes, so unless you have a laboratory onsite, then you will need to use either litmus paper or a calibrated pH meter to run the test in the field. Over the past few years, we have witnessed increasing issues with faulty litmus paper giving readings that are not accurate, causing facilities to exceed pH ranges set forth by their stormwater permits. Along with litmus paper giving incorrect readings, it is also very open to interpretation based off of the person conducting the color-matching, and if you’re color blind forget about it!
Due to the multiple reasons that litmus paper can cause problems with obtaining correct readings, we always suggest utilizing a calibrated pH meter. The keyword here is calibrated, without proper pH meter calibration, you will run into similar issues with incorrect readings because the meter will not understand what the correct ranges and reading are. When calibrating a pH meter you want to make sure that you are using a three-point calibration, not just a two-point. This means that you are calibrating the meter to read three buffer solutions; 4 (low range – acidic), 7 (mid-range – neutral), and 10 (high range – basic). If you only use two of these buffer solutions (i.e. just 4 and 7) then your pH meter will not get the full range of readings and will likely read more acidic or basic than the actual stormwater sample.
Calibrating a pH meter can be tricky. To help simplify this process for you, we’ve made a lovely “How to” video to guide you through the calibration process. If you would prefer to hear the instruction in Spanish or Vietnamese, you’re in luck! Check out our pH meter calibration video in all three languages below!