Grey Pool Water

by Mike

Have been working on 27' x 52" round above ground pool for 2 weeks. Background: pool was uncovered for winter and had a large amount of leaves in it and was completely green. I mean it had the thick mucus green algae. I have removed the leaves. I have dumped (2) different algae bombs (enough for 50k gallons of water.

4 gallons of liquid chlorine and 2 water clarifers. My test numbers this morning are as follows; ph=7.8 chlorine=10 alkalinity=120 stabilizer=20 I have vacuumed 2 times. I now have grey water for the last 2 days.

Not clear, not green. What do I need to do?

Thanks for the question Mike

First you need to understand that you only need to bring the chlorine up to 12 - 15ppm for a good shock. Anything more than that and you're not only wasting chlorine but you run the risk of slightly bleaching the liner.

Shocking is a process, not an event. The trick is to get AND keep the chlorine above 12ppm for a period of time. You'll need to manually dose the pool with chlorine to keep it at 12ppm. Make the adjustment at night, retest in the morning, and make another adjustment. Be sure to have the pump running 24/7 and backwash once per day.

You'll know this is working because the pool will go from green to a white/grey cloudy and the chlorine will begin to hold better. First you may lose most, then 2/3, then 1/2, and so on. Once you only lose 1 - 2ppm of chlorine 8 - 10 hours after the last application you know the algae is dead. Now it's just a matter of filtering and backwashing once per day. Broadcast the chlorine around the perimeter of the pool and brush well. This will loosen up any algae adhering to the walls and bottom.

Lay off the clarifiers until the very end. They really do nothing during the shocking process. Only use it after the water is white. This is when the algae is dead.

You need to get some acid into the pool to lower both the pH and TA. Chlorine works better at a slightly lower pH. You pool is about 21,000 gallons, right? You use 0.8 qrts. of acid to lower the pH 0.2 per 10,000 gallons. Start with
about 20 oz. of acid. Broadcast around the perimeter of the pool, sweep, and FILTER for 10 hours, then retest and make another adjustment if needed.

Next is the CYA. It's a bit low at 20ppm. The correct range is 30 - 50ppm. Use 25 oz. of straight CYA to increase the CYA 10ppm per 20,000 gallons. Same technique as above.

Here's a pool I recently cleared up for a friend. It's almost the exact same situation as yours:

If you feel your situation is more complex and want immediate assistance (within 24 hrs) you can make a donation of your choice and I'll answer your questions by phone.

Have a great Summer.


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