Rgirard

Sorry. Yes I meant CYA. I am in Las Vegas and we do have that hard water. By way over I mean when I use my test kit with the small black dot at the bottom, I get about 1/3 way to the beginning of the scale before I can't see the dot. So even though I'm putting chlorine in with a high CYA it will show 0 chlorine. Thanks for the help with the Pool School. Very informative. I used to have a pool company maintin the chemicals, but they got out of hand price wise with constant fee increases. I get to do it myself now.

Hello all: I know the answer to the question, I just don't know why. I need to drain the pool and start over. My pool has not been drained for 4 years and the CA level is WAY over 100ppm. I'm sure the TDS are way over as well. The story: At the beginning of the season I didn't bother measuring the CA level. I just added chlorine and pH balance to get within the correct levels. All was well. Beautiful clear blue water. Then the weather got warmer and all of a sudden the chlorine crashed and the algae started in. I did a CA test and found it to be way way past 100ppm. Everything I have read indicates that my chlorine levels should be off the scale in "Chlorine lock" but my testing indicates 0 chlorine. Why is that? Also, is 4 years a reasonable amount of time to have to replace water. Again, from all I have read it seems to take a few years longer before the CA or TDS get to the drain and refill point. Thanks in advance for your help.