First off, I want to welcome you to our forum. Unfortunately, there is no way to know which pool store's readings are correct. That is why we advise buying a good test kit and testing your own water. We recommend a Taylor K-2006 or 2006C. Then you don't have to rely on pool stores. The kit is a little pricey but it will pay for itself in no time and help you avoid cloudy water and a whole host of other problems as well.