Cloudy Pool Won't Clear

by Linda Palmer
(Baker City, Oregon)

I opened the pool three weeks ago (mid May)after a much warmer than usual winter. It was full of algae so I shocked it heavily until the green color changed to blue. There remained lots of clear dead algae slime which filtered out after several days. The pool was still cloudy.

I added clarifier, no results. I changed the sand in the sand filter (it was 19 years old!) No results. That was one week ago.

The filter has been running nearly continuously since then, but the water remains as cloudy as ever.

Test results from home kit:
Chlorine: ~1 1/2
pH: 7.5
Alkalinity: 40
Hardness: ~ 150
Cyanuric Acid: 30-50

I would appreciate any insight on this.

Thanks for the question Linda

The first thing that jumped out at me is the low alkalinity. It needs to be between 80 - 100ppm. 120ppm being the top.

You can raise the alkalinity using baking soda. Add it in the deepest part of the pool with the pump off. Allow to sit for 3 - 4 hours, turn the pump back on for 8 - 10 hours, then retest and make another adjustment if needed.

Use 1.5 lbs. of baking soda to raise the alkalinity 10ppm per 10,000 gallons. Start with maybe a 20ppm increase and work up. Don't go all out and try to fix it at once. It may take a couple of applications before the proper range is reached. You may overshoot the mark, then need to add acid to bring it back down. Again, another added expense.

The other readings, except the chlorine, are perfect.

Now for the clarifier. Basically, you don't need it. It's another expense and, for the
most part, useless. It doesn't address why the pool is cloudy to begin with.

Most of the time when a pool is cloudy, it's an early sign of an algae bloom.

The trick is to get AND keep the chlorine above 10 - 12ppm for a period of time. You'll need to manually dose the pool with chlorine to keep it at 10 - 12ppm. Make the adjustment at night, then retest in the morning. Be sure to have the pump running 24/7 and backwash once per day.

You'll notice the chlorine level will start to hold longer and longer. It must if the pH is 7.2 - 7.8, TA between 80 - 100ppm and CYA between 30 - 50ppm. Be sure you're using enough to get to 12ppm and not too much more. There's no chlorinating difference between 15 and 20ppm, only the amount of chlorine used.

Green Pools

Start manually dosing with chlorine each morning and evening to keep the chlorine above 10 - 12ppm. I'd shoot for 12 - 15ppm, but not higher. After each shock you'll want to sweep the pool very well.

1 gallon of chlorine per 10,000 gallons to reach 10ppm. This takes consistency and patience. Remember that shocking a green/cloudy pool is a process, not an event.

If you have a vinyl pool, you may want to first mix the chlorine in a bucket of pool water, then broadcast it around the perimeter.

I can't say how long it will take before you have a crystal clear pool, but I can tell you that I've personally used this process hundreds of times to clear up green pools here in Oregon and on my pool route in Arizona.


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