It had been a relatively event free first winter managing my first pool here in AZ. Relative to summer, chlorine demand went down to almost nothing with the shorter days, lower temps and no swimmer load. I'd almost say it's been on cruise control.
Then a couple weeks ago we had a big wind storm. And the tree near the pool has been dropping a lot of tiny yellow flowers in and around the pool. And I got complacent and didn't get the organics out ASAP. And my complacency continued with a lack of proper testing. And then it started getting warmer and the days longer. And then I walked out last Wednesday and the pool had an odd green tint that I'd never seen before.
So I grabbed a sample and FC = 0. Uh oh - I've got my first algae bloom. pH was about 7.5. So I added a bit of acid before I started the SLAM. TA = 90 & CYA = 70. (CYA has been drifting down with filter back washes since we got the house back in July) I didn't have supplies on hand that night, but I added the last gallon of 8.25 bleach I had on hand. Within minutes the green had faded to whiter and cloudy. A gallon of bleach is worth about 6 ppm FC in my pool (ignore my volume below - that was a best guess).
With my CYA, the chart calls for FC of 28. So I loaded up on bleach and got to work. I kept the FC over 28 and vacuumed a couple times. Backwashed after vacuuming and kept all the baskets clean. Pool steadily looked clearer and clearer. It looked essentially normal yesterday so I decided to give the OCLT a try.
Last night at 6:40 the FC was 29 and then 28 with the same sample. CC is just barely pink on both - >0.5. This morning at 07:00 the FC was 27.5 & 26.5 again with the same sample. No CC to be seen. The test says I need to have a FC drop of 1.0 or less. And with the variability in my testing and depending on how you read the numbers, you could say I'm good (best case) or I still have a demand of 2.5 (worst case). Average would be an FC loss of 1.5.
Any advice? Again, water looks clear. Call it good? Give it another day and try again?
I guess my problem is the variability in the testing. With a 10 ml sample, it seems like it's difficult to be exactly consistent enough when testing at FC levels this high. A tiny bit of variability on the sample size (or drop size) seems to impact the readings by at least 1.0 ppm. I don't want to go to bigger samples for accuracy because I can't count that high with drops.
Any input would be appreciated.
Oh - and the obvious lesson I learned is that I can't get complacent. I need to stay on top of things and temps move around and days get longer. And do a better job keeping leaves and such from accumulating.