When Pool or Spa Total Alkalinity is low it can be difficult to get the pH correct and rapid changes in the pH can occur for seemingly no reason. The pH and chlorine testers often show an incorrect level as well. To truly get the best out of your pool or spa it is recommended that you firstly get the total alkalinity (TA) of your pool or spa correct. It will then allow you to set the ph and chlorine much more accurately. The Total Alkalinity should be between 80-140mg/l (ppm). Full instructions are included. Most test strips have total alkalinity testing, so it's easy to test for!