Algae won't go away!

[amajidi]

Hi,

I have been battling the alage. Ive had a blue clear pool for about one week this summer. We have ha d a lot of rain and it's been tough. I attached my results below from he other day. Looks like I need more cya, chlorine, and calcium. High phosphates too. I added shock and phosphate remover PR 10,000. After running the pump for at least 12 hours x 2 days and brushing the pool, there was a thin layer of green algea all over the pool this am. I tried to vacuum and it became cloudy with a hint of green now. Can someone please advise? Last year as long as my chlorine and cya was good I had a crystal clear pool. Any ideas?

Thank you,
Abdullah [img]https://uploads.tapatalk-cdn.com/20230701/a28be353c1580d1afe0a24dbb6312da2.jpg[/img]

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[amajidi]

Pool is about 30k gallons.

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[UmmScott]

CYA is too low.
Free chlorine is too low...
You have combined chlorine.

You need to elevate your free chlorine levels and maintain them high until you have near 0ppm of combined chlorine.
It's called the SLAM process

Others will chime in that know more than I.

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[Denniswiseman]

With a CYA of 20 you need a minimum of 2ppm of free chlorine and a target of 3-5ppm and a SLAM of 10
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[Teapot1]

SLAM, shock level and maintain. You may be losing chlorine to the suns UV a little quicker due to a slightly low CYA level. You mainly need as previously posted to increase your free chlorine level to around 9-10ppm at which point the algae will die and the water will turn blue/grey and cloudy inside an hour. This killing of algae quickly uses up the free chlorine so you need to add additional amounts to keep it nearer 10 for a while until your water is clear and overnight chlorine loss is minimal. Then you can go back to normal levels of chlorine in your case 7% of the CYA level. 21ppm x 7% = 1.47ppm free chlorine (this is your minimum figure) due to your high phosphate level if you allow the chlorine level to fall below this algae will quickly return as phosphate is an abundant food supply for algae.

[amajidi]

Thanks all. So I should shock and maintain a level of 10ppm total chlorine until the water is clean and clear then maintain a level of free chlorine at 2-5ppm (never under 7% x CYA ~1.47ppm). Did I understand this correctly? Should I add CYA first to raise it since I'm at 20 and ideal is 30-50? If yes, when should I add it? Afterwards, the idea is to shock and maintain that free chlorine level, right? Also, does it matter if it's liquid shock or powder? Thanks for all your help!

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[Teapot1]

No 10ppm of free chlorine, total chlorine is free chlorine + spent chlorine, you could have 9ppm of spent chlorine and 1ppm of free so you can see thats no good at all.

No dont raise CYA now, deal with the algae issue. Add CYA from pucks later. Shock at dusk to avoid losing chlorine to sunlight.

[Denniswiseman]

Thanks all. So I should shock and maintain a level of 10ppm total chlorine until the water is clean and clear then maintain a level of free chlorine at 2-5ppm (never under 7% x CYA ~1.47ppm). Did I understand this correctly? Should I add CYA first to raise it since I'm at 20 and ideal is 30-50? If yes, when should I add it? Afterwards, the idea is to shock and maintain that free chlorine level, right? Also, does it matter if it's liquid shock or powder? Thanks for all your help!

Use liquid chlorine to get virtualy instant results

[amajidi]

I started the process tonight. I brushed the pool and vaccuumed. Backwashed. My FC level was 5. I used the pool math calculator by TFP (to get to 10) and added 1.5 gallons liquid chlorine . So I should check the FC in the morning and at night and add to maintain the 10 until clear, minimal loss, and CC <0.5. How soon after adding should I check the FC level again or just check before and add according to the calculator and don't check until 12 hours later? Thanks.


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[Teapot1]

Thats about right, if you are doing the overnight chlorine loss then before the sun comes up strongly. A bit early to do this just yet, maintain your shock level for a while and keep brushing.