Thanks, what level of cl will give more accurate pH reading? I do believe that it is high though since I've been running the swg on 70% for about 20 hours a day for a couple of weeks and even at 8 hours a day I usually have to add acid weekly, especially with the TA being above normal. I do need to test my fill water. I use water from a shallow well we use for lawn watering. I do know that it has sulfur in it but I'll need to check the calcium. Metered water is a bit expensive so I use the well since it's free .