Chlorine demand change

[H-12 1/2 Mike]

Over the last week I have noticed a drastic change in my chlorine daily demand from 32oz of 8.75% to 97oz per day. The CYA has been a constant 50ppm. I have been checking and recording daily for the past three years and have no record of this drastic change occuring before. The water temp has dropped only 3 degrees in the last week. I have cleaned my cartridge filters in the last week. I have increased my pump rpm from 1500 to 2000 in the last week. My pump runs 24/7 and has for several years. One other change has been that the waterfall is now running 24/7.
Any ideas?

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[duraleigh]

Chlorine is lost from your pool either by UV from the sun or living organics in your pool........nothing else.

Since your UV loss is stable and actually decreasing a bit as the sun gets lower, the inescapable conclusion is you have invisible algae and need to SLAM your pool.

 

[H-12 1/2 Mike]

Thanks for the information. I will slam after a couple of days of monitoring to see if it will stabilize. The water is perfectly clear and we do have a lot of leaf drop at the present.

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