Hunger for chlorine after changing pool water ...

Is it just my imagination or does my pool need more chlorine more frequently after I changed the water?

We moved into our current house in Arizona in 2001. At that time, I remember putting five 3" tabs in a duck and pouring two quarts or so of chlorine into our 22,500 gallon pool every two weeks and the chlorine would stay around 1.5 to 2.0 ppm nicely.

Then, in 2005, we changed out the water (that's how I know I have a 22,500 gallon pool) and it seems that, ever since then, my pool has become much more hungry for chlorine.

I put in cyanuric acid, as recommended, and have been using mostly tabs of tri-chlor (essentially cyanuric acid with chlorine rather than hydrogen attached to the three nitrogens) rather than liquid chlorine.

Now, when I shock with eight gallons of liquid chlorine, the level of chlorine will drop to nothing within 36 hours (in at 9:00 p.m. tested at 9:00 a.m. 36 hours later). Also, if I distribute four pounds (eight crushed one-half pound tabs) of tri-chlor, that too is gone within 48 to 60 hours.

Because of this hunger, I now do "shock and glide" cycles rather than trying to keep the water at 1.5 ppm to 2.0 ppm constantly.

My water is crisply clear and there isn't any visible algae.

Is this normal?

Thank you!

If you didn't add stabilizer . . . yes, chlorine use on an outdoor pool will be out of sight. If you did add it, unless you used 'liquid stabilizer' it takes several days to dissolve. If you cleaned your filter first . . . well, you can work that one out. It sounds like you may have had very high stabilizer before, and now have rather low levels. The high CYA would explain your need for copper -- see the "Best Guess" page below for an explanation and info on how to adjust. The low CYA now would explain current results. (You probably have some CYA -- in full sun, with NO CYA, you can lose all your chlorine to photolysis in a few hours.)

Get a K2006 (the C model is a better deal -- Amazon links below, but order ONLY from seller "Amato Ind") and learn to test it yourself.

Ben

PS. Sounds like you may have bit of chemical knowledge. Read the basic functional pages first, so you can take care of your pool, but then you may want to take a look at Chem_Geek's pages in the China Shop. Currently, he knows more about pool chemistry, from an analytical point of view, than anyone else in the world. I mean that literally, not hyperbolically. There are some chemists scattered around the industry who know more about bits and pieces of it than he, but no one knows more about the whole system.