Algae Bloom

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Plankton

Well-known member
Apr 13, 2008
94
Hi All,
I've been a member of this site for quite a while and although I don't post much I read everything I can when someone has a problem, so I've learned quite a lot. I stopped using pucks over two years ago on advice of this site and went to the BBB method. I am very happy with it. So as my title states I've had an algae bloom ( I'll tell you how I got there in a moment) and just want to check with you to make sure I am doing everything right. (I have read all the articles in Pool School and just re-read them again) The following numbers are off a TF100 test kit (another lifesaver):
Pool Size 17.5K In ground Pool with a 2.0 HP motor connected to a Purex Clean & Clear Plus Cartridge Filter
FC-11
T/A 90
CC-0
ph-7.6
CYA 70
CH 500 (I know, way off)

So I have continued to brush every couple of hours and earlier today got my FC up to 28 (Shock Level) based on my CYA levels. This number I got from using the Chlorine/CYA chart. The last reading was tonight and that was 28. Filter running now 24/7, water is cloudy, and I am in the process of accomplishing the Overnight test tonight, just want to make sure I am on the right track. Please let me know if there is something else I should be doing.
Now for how I got to this situation, I was keeping my FC at 5ppm which is what the calculator stated I should be at, I installed a solar cover and while the deep end of the pool was crystal clear, because that's where the Polaris was, when I removed the cover at the shallow end there was green everywhere, is there a problem I don't know about with solar covers? I was really heating up the pool and cutting down on the addition of chlorine along with my water evaporation. I would like to continue to use the cover, but not at this cost. If anyone who has been through this can give me some advice it would be greatly appreciated. Thanks!
 
I am pretty sure the solar cover is not going to increase the chances of getting algae. If you got algae it is because your chlorine level dropped below that required for your CYA level. Are you manually dosing? If you are then you should really keep your chlorine level closer to 8. 5 is the minimum for a manually dosed pool.
 
The FC has been maintained too low.

For 70 CYA, the FC should be beetween 5 and 10, and never below 5. As benavidescj suggested, maintaining closer to 8ish is the goal.

You are on the right track with the shock process. See red lines in my sig.
 
Plankton:

The solar cover can help reduce FC UV loss so you might not have to add as much chlorine. However, somewhere along the way, the FC likely dipped below the target level for your CYA, even for a short time. Another possibility is that your CYA is slightly higher than 70. Per the Pool Calculator, a one point increase in CYA to 71 bumps the minimum target FC level from 5 to 6. Even though I test in proper lighting, I aim to maintain a minimum FC level at least one point above the minimum for my CYA as a buffer.

The CYA test is perhaps the most subjective test to measure. Proper lighting is critical. May be worth your time and reagent to retest following these instructions: http://www.troublefreepool.com/extended-test-kit-directions-t25081.html - scroll down to the post "CYA - Cyanuric Acid"
 
Thanks everybody for the replies, so to answer a couple of questions I manually add 10% chlorine and was keeping it a 5ppm, obviously that was on the low side, and I must of though I was correct, i probablty read through the chart too fast, saw 5 and thought it was correct, my bad. I read through it slower again and saw the 8 to 9 ppm now and that is what I will be keeping it at once I get through this. I did my CYA test three times yesterday and another 3 times today, so I am confident I am at 70ppm, help in the sunlight, wore my glasses, did everything by the book both times, that is one really hard test, especially when your eyesight is going wacko on you to begin with!
BoDarville- good advice, I will do that from now on, thanks!
I did the overnight test last night and lost 2ppm, so it's not all bad, hopefully I'll be able to get a handle on this pretty quick. Thanks again for the insight from all of you!
 
Plankton:

Thanks for the update.

You may already know this, but just in case...

Since you lost 2 ppm FC on the OCLT, you need to continue the shock process until:
  • CC is 0.5 or lower;
    An overnight FC loss test shows a loss of 1.0 ppm or less;
    And the water is clear.

Sounds like you are getting close!
 
Will do! I will keep you guys/gals updated as to my progress. I didn't get to check my FC last night as I was out all day and most of the night due to the 4th, so I am resuming everything today. Although it does look like it's getting much better, at least it looks clear now, not crystal like it should be, but clear, that's a plus. I also have a lot of patience just due to the fact it was my screw-up, oh well live and learn.
 
If the problem happened soon after adding the cover, then the cover may have been dirty and it used up chlorine in the vicinity with the water near the surface. If the returns weren't pointing upward somewhat to give a good water flow, then algae may have grown there and depleted more chlorine. The FC minimum for the CYA level is when everything is in a good steady-state. If you introduce something into the pool that consumes more chlorine, then the FC can drop and algae can then grow faster than chlorine can kill it. Also, warmer water uses more chlorine (all reactions are faster) and chlorine also reacts slowly with the pool cover itself.

I had a somewhat similar situation happen to me years ago when I turned on my solar system during spring startup but didn't add more chlorine so it got to zero and I had bacteria convert CYA into ammonia. I was figuring on a steady chlorine consumption instead of realizing that the solar tubes were probably not clean having been shut down over the winter (and though mostly drained, they aren't blown out so algae and bacterial biofilms can still form).
 
Chem geek- Very good point!!! Ya know I thought about that when I put the cover on, but it was one of those, "are you oversimplifying this????" Now I realize I wasn't LOL!!! But my returns are all pointed upward anyway, but as you and everyone else stated, it all boiled down to not enough chlorine in the pool. Thanks Again!
 

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Hi All,
Just an update, my CC's are at 0-.05 and the night before last (7/7) my FC dropped 2ppm. I am still at shock level at 28.5 and did another CYA test this morning just to be sure. I am pretty sure I am at 70, actually 60, is what I read three times and had my wife double check the reading, but that can't be right because CYA doesn't go down, it goes up. So at best I am at 70, no higher. So my shock level at 70 is 28 per the chlorine chart. I will do the overnight test again tonight. The pool water is looking much better though, not so milky anymore. A question though, should I add acid for my ph level? I know the ph reading is inflated due to so much chlorine that has been added, so should I wait or continue to add my normal dose of acid and take the readings. Thanks
 
benavidescj said:
You should not adjust pH while shocking because the pH test doesn't work reliably when FC is above 10. Normally what happens is you adjust pH prior to shocking and then wait till shocking is complete to adjust the pH.
Click to expand...

Ditto. Well said and dead-on accurate.
 
Okay, that's exactly what I did before I starting the shock process, just wanted to make sure I didn't misread something in Pool School before I started. PH was 7.6 so that was just out of limits by a bit but close enough. Didn't get to check the FC last night, got home way too late from work to want and go out to the pool at 2am and take a reading, but took one this morning and within a 24hr period & I only dropped 2.5ppm, so that's a definite improvement compared to what I was dropping in a 12 hour period. I also took out my pool light fixture and cleaned behind that and changed the seal since I could see bright green algae growing there. Once I got the seal off there was a lot of algae on the inside of that seal, so I'm glad I did that, I think it helped quite a bit. Next will be the spa light cavity and then the pool is done. All I'll have to keep doing is brushing every day and wait until I meet the parameters of the shock process. Hopefully that will be this week, cause it really is heating up here!
 
Just an update for everybody who has helped me on this, I have had success!! and failure, but first the success, the over night FC reading has been consistent for two nights now, no F/C loss for 8 hours (midnight until 0800) CC's are 0 and pool is clear! I'm happy about that. I'm just waiting now for my F/C to drop to normal levels, because even sticking my hand in the pool makes it come out really dry, but I can live with that for now. Now for the failure, I pulled out my Spectrum/Amerlite Color Light to clean behind the housing/niche and the light itself because my chlorine was not stabilizing on the first couple of overnight tests. The lens seal had bright green algae in it and the niche had algae in it too, cleaned it out, replaced the seal, put it back in, tested it and it worked. I came home the next night, grabbed a beer (0100) and went to sit out by my pool and admire it, turn on the light and it was this yellowish almost sort of incandescent color, just didn't look right, I had a bad feeling and hoped it was just one bulb burnt out( yeah right!). So pulled out the housing the next day and it was half full of yellow water with what looked to be lots and lots of algae, weird, but just below the lights. Emptied it out, cursed the dreaded pool store for the seal they sold me, pulled the lights and tried the color wheel function, no work:) Lights do work though. Great, just great I said. Now I was even more P.O'd at the pool store, so I put the original sea, put itl back on and let the housing sit in the water for about an hour, guess what? More water in the housing.( I apologized to the pool store under my breath LOL!) Since I had been through this before with my spa light I knew exactly what was going on, when I removed the light assy for the pool which had not been touched for 12+ years, I must have disrupted the cord in the back and broke whatever little bit of seal that was left allowing water to enter the housing. So now I'm in for a new $500 plus light fixture. I've reviewed this and although I can replace the motor it's not going to help, someone already tried that and at least saved me $50 plus shipping on that. So here's my question, I'm pretty good with mechanical things, and pretty good with electricity, but although the lights in the housing where not immersed in water( I don't think they were but they were pretty darn close) the GFCI did not trip, question is why? It's always tested before we enter the pool. It trips and the pool lights go off as they should. It was replaced three years ago, so do I have a problem? What else should I check to verify it is working properly, any help would be greatly appreciated.
 
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