An unexplainable algae problem.

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bobjdan

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Aug 5, 2009
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Raleigh, NC
Pool Size
25000
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Vinyl
An unexplainable algae problem.

On Sunday 11 I1 tested my FC and it was 4.5. I didn’t test it again on Monday morning because it had not been dropping because my water temperature was 57.5 degrees, it was raining , I had no chlorine on hand and was getting some on Monday. However, I did walk by the pool later in the day and it was clear. Anyway it rained most of the day Monday and part of the night, a total of almost 5 inches. Tuesday morning I looked out and saw the green water. I tested the water (I use the TFT-100 test kit) and the pool calculator to maintain my pool). Okay, my bad. In retrospect I should have gone to the store Monday and got chlorine but was too busy with other things. and it was raining. That is not what this is about

My CYA is in the 35-40 range and at 40 the recommended range is 3-7 depending on CYA. Tuesday morning I tested the chlorine and it was 4. PH about 7.4. I found that strange because the algae had eaten little or no chlorine. Because of prior commitments and no chlorine on hand I didn’t begin treatment until 4 pm. FC was still 4 and suggested shock is 14-15 depending on CYA. Suggested chlorine was 3 + gallons and I added 4 bottles. I tested at 6 and FC was 15. Since it was dark and raining a bit I added another 121 OZ bottle. Wednesday morning it was 19, i.e. no overnight drop. I use HDX Germacidle Chlorine 121 oz. 7.9% available chlorine.

Since that initial 3+ gallons I have only added 3 gallons. On 1/18 8 at 8:30 a.m. it was 17 but
since it had been sunny and warmer the day before and the same predicted I added another gallon which normally raises FC by 3 ppm. I tested it at 4:50 pm and it was 17. On 11/19 a.m. it was still 17, no overnight drop which should mean the algae is gone. However the water still didn’t look quite as clear as normal, slightly milky looking. I checked it again in the a.m. on 11/20 FC was 14. Still looks a bit hazy. This a.m. 11/21 it almost looks like it has a very slight green tint. FC is 12.5.

A few strange things about this bout of algae besides the cold temperature. I have kept my pool in the 3-7 range for many years. At onset it wasn’t very green, I could still see the white main drain cover. FC dropped only .5 From Sunday's 4.5 to Tuesday a.m. 4.0 After shocking for 2 days I could still not see any dead algae when I brushed the pool 2 days later or now. I could also see no change when vacuuming. I just had the filter sand a few weeks ago and I can see no increase in pressure. I’ve been running the pump 24/7 since onset.

In the meantime I guess I’ll go to HD, get some chlorine and hit it at a higher level longer until clear?. Any other ideas?

Thanks and happy TDay.
 
Pool deep end horizontal.jpgShallow end horizontal.jpg

I took the pictures about 11 a.m. today and I don't see anything resembling a greenish tint that I thought I saw at 8:30 a.m. now that the sun is on it. In the sun it may not be easy to see the difference but both my lady friend and a guest we had for lunch said the deep end looked cloudier/hazier than the shallow end. The deep end usually looks the same as the shallow end even though it has more stain.

You are right that it came on quickly. The last time I had algae was almost identical and that was the last time a hurricane at the coast dumped a lot of water in overnight. I posted it then and it is still around but I don't know how to find the link without getting out of this post. I'm sure you can or I can and post it if you want it.

Thanks.
 
aussieta said:
was the cya test performed correctly
bright sunny day, solution at room temperature, vial at waist height, back to the sun
and the one ingredient most of us are guilty of brushing regularly
Click to expand...

I took the cya reading at the edge of the deck in natural cloudy light. If the light had been brighter I would have had an even lower reading, right? I hear you about the brushing which I did after 2 days and I'll do it again Friday after slamming it again tomorrow.

Thanks.
 
I had pretty similar experience about 2 months ago. As I was getting ready to close my pool, I had it covered with solar cover for a few weeks. Everything seemed fine. I was only loosing about 0.35 ppm FC per day. My pH stayed at 7.4 and CC was 0. With such minimal chlorine loss I got comfortable and was adding and testing chlorine every 5-6 days. However for my CYA of 30 I never let FC drop bellow 2.5. Just as I was planning to close the pool I took off solar cover and found a lot of debris/sediment on the floor of my pool. It looked like kind of like a mold and dust/sand. Water had a green tint but was mostly clear. I made mistake and put my robot in to try to scoop some of it. After my robot stirred for a while water turned into deep murky green. I couldn't see anything in it anymore. I was surprised to find water still had 2.5 ppm of FC and 0 CC. I SLAM it and about 10 days later my water become crystal clear again. However I noticed there was spots in a pool where something resembling dust would collect in a little creases of vinyl floor. They would vacuum easily but would reaper a day or two later. In retrospect I remember seeing something like that before my algae bloom happened. That got me thinking it might fave been mustard algae which is pretty chlorine resistant, so it would explained how it bloomed even as chlorine was still present and in within recommended levels. I ended up raising chlorine to mustard algae level for 24 than I let it drift down to normal shock level and I closed the pool as freezing temperatures where expected. I guess I'll find out in a spring how successful it was. Bottom line: I found out it's possible to have algae bloom even with minimal chlorine loss and 0 CC
 
I had mentioned that my cya was 35-40 looking at it under cloudy conditions. Yesterday I checked it under sunny conditions as suggested by Aussieta and it looks like 0. I don't know how that can be since I used about 9 of those pellets while traveling within the last 9 weeks. At 0 the pool calculator says my shock level is 10. I raised it to 20 yesterday (sunny) and it was 17 this a.m.. Still looked cloudy.

Thanks.
 

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9 tablets of Trichlor would have raised your CYA by 12 ppm in your pool. Use Effects of Adding Chemicals in PoolMath.

It would be best to add 20 ppm of CYA powder using the sock method and get it up to a readable level. The use of liquid chlorine without CYA in a vinyl liner pool risks significant fading of the liner.
 
Unfortunately I didn't know the suggested way to use the CYA test as described by aussieta above and I'm afraid that my liner has now been bleached. That may also be why my pool water looks different than it did before because my bright blue patterned liner is now a mostly solid pale blue. I added CYA powder as suggested by mknauss and yesterday it was somewhere between 30-40 as read differently by myself and girl friend. I should have guessed it was lower than normal because I had been using more chlorine than last year but still don't know how it got to 0 since I had added a total of 5 lb. 3 inch tabs over the summer.

I'm still not sure the water looks like it used to before the algae but with winter and overnight freezes coming into the mid-20s I closed the pool yesterday. There was no overnight FC drop. FC was 14.5, CC 0, and water temperature 53. It will be interesting to see the water color when I take off the cover in April.

Thanks to all that responded
 
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