Ready to Fill it In!

[Ray]

Well, your pool dealer is incorrect. Chlorine lock may be a poor term to use, however, it has been proven time and again that CYA levels that are too high reduce the effectiveness of chlorine. You get to a point that the "normal" ppm of chlorine is doing nothing for your pool. You will fight a losing battle and see faster recurrances of algae.

The more pucks and pool store shock you use, the higher the CYA will get, causing even more of a problem. Good luck with that.

Given that how often should one change the entire pool water content (or a significant fraction thereof?

[Buggsw]

Ray, so much depends on the pool, location, fill water, costs, environment and many other things.

If your CYA gets over 50 ppm, you should stop using stabilized products.

However, most people don't know about this and continually use stabilized products and often get over 100 ppm to 200 ppm. It's real easy to do.

You can do one of two things at that 100 to 200 ppm point. Use a ton of unstabilized chlorine regularly and keep your chlorine ppm at 8 ppm for swimming and shock at least 25 ppm. Or start, dumping or vacuuming to waste regularly and refilling to hopefully get your CYA down.

If you let your CYA get to 100 ppm you'd have to dump half your water to get to 50 ppm, if your fill water had no CYA in it (which most fill water does not)