First, a confession. After taking over the pool in April, I used all of the help here on the board to get everything balanced nicely. Maybe a little too nicely, as I soon settled into a routine where I made slight adjustments automatically to my chlorine withour everyday testing. I simply used the prior changes to guide my additions of approximately the correct amount of chlorine. Now, in June, we have steady 90s degree weather and the pool temp is about 88. In my short cut, I failed to consider that much warmer water combined with full and strong sun would change the rate of chlorine usage.
However, I am now paying the price for this laziness as I noticed a couple small green spots in the pool while brushing it 2 days ago. Algae! I probably wouldn't have even noticed the small spots if I wasn't brushing and regularly looking things over. I took a quick reading and had FC and CC both at 1, while pH was up to 8. I added a full gallon of Menrad's 12% liquid chlorine (given my 30,000 gallon pool should have moved the FC up very considerably), added muriatic acid, and hoped it didn't get too much worse over night. I should note that the water has remained clear throughout as I think i reeally did catch this very early.
Yesterday I brushed again as things looked to be improving (many of the green spots were now grayish black and began to brush away) and I anxiously awaited sundown to retest levels. Here's what I got....
FC = 2.5
CC = 0.5
pH = 7.2
TA = 90
CH = 280
CYA = 70
Again, based upon my pool and a desire to knock this bad boy out, I used the Pool Calculator and saw that shock level would be 20, given my situation. Basically, as I read the Calculator, I again needed to add another 12% gallon. I added it last evening and looked forward to what today would bring.
Bright and early today I examined the pool. Water still clear, green spots mostly faded, but a scattered few remain. Then I did my water tests. Here's what I got...
FC = 6.5
CC = 0
pH = 7.4
I am having very mixed feelings. First, I am glad that I am getting a "0" reading on my CC, but given the fact that I still have a few green spots I question this. I also question why my FC would only be at 6.5 when I'm thinking it should be at least in the teens.
Am I doing the tests wrong? Is there a way to check this? I know that I have stubbed my toe a few times trying to use the Calculator so maybe my inputs or conclusions are wrong from the caluculator. Otherwise, could my liquid chlorine have degraded in potency while being stored? Not sure where I go from here, other than to keep brushing and get a few gallons of standard 6% bleach and see if it makes a difference. Any thoughts, comments or suggestions appreciated. Thanks.