Casey74

Hi, bro sorry about making use of ur thread here but since all of u are talking about calibration, I have a question here, that is, when I do calibration of the PH pen to 7 and use it to test my water. After that, when u take out from the water after testing, will the reading go back to 7 again or must I everytime had to do calibration when I want to test water again?

Please advise. Thank