Thanks for the reply Wildcat and Tim. The reason I do not think the FC dropped below 2 is that I test FC at least 2 x/day sometimes 4 depending on what is happening. I test FC before adding chlorine, so the lowest FC I ever had was 2.5, if it went lower it would have shown on testing. I know it is a lot of testing but between myself, wife and other family members we can do it. I test early in am before work and when I get home or before bed depending on if the solar cover was on or swimmers, etc. So if it got lower I would have known it unless there was error testing when it was low. The reason I have been testing so frequently because I know I have a low CYA (it is 30) is because I will be using Trichlor feeder when we go away for a week soon and that will take it up to 40 perhaps 50. Last year when I had it at 50 I bought a solar cover and using the solar cover, developed an algae bloom and it was more of a pain to SLAM at 50. I do believe 30 is correct my wife reads pretty close to the 30 line, I read as about half way between 20 and 30 which would then be read as 30 anyway. So if anything I think it may be a little under not over. I also bought a 50 reference so I would know more of what it was supposed to look like at a given level. Another reason I test frequently is I am using solar cover again and wanted to monitor closely. last year I did not take light out of niche, when I used cover got a bloom. this year I took out light and there was a lot of black algae in the niche, so I really inspected the pool found a very small bit of dried green behind the rubber ladder rest, cleaned that and scrubbed both returns very well when opening. But I will leave the possibility that there is someplace algae is was lurking as a reason for the bloom. Also the solar cover gets very dirty which ends up going in pool and in reading some old threads on solar covers it appears to be a moderately common problem but many use solar covers without any problems so I am thinking I am missing something just do not know what. I am also trying to stay pretty close to target # on charts for chlorine as it is fairly caustic and can decrease a solar covers life span (as well as bathing suits and other pool objects) if you go higher according to a post I read by chemgeek who I highly respect. so I am trying as best I can to keep the FC close to target level. Last year before I got solar cover I got so I could control FC testing 3-4 times a week and just adding a set amountof chlorine but this year with so many variables I wanted to keep as close an eye as possible so I know better what is happening. I want to update with a more automatic system such as a pump or SWG, just not really sure of which one and hate to spend all the money and then wish I went the other way, but summer is passing fast. The last area is circulation which may be a problem, especially with a solar cover. But I bought a robot this year and I run the pump 8 hours during the day and then usually 2 cycles of the cleaner at night which also shoots a lot of water around to increase circulation when pump not on. When I inherited this pool it did not have any eyeballs on the returns and I did not know I needed them but in researching this year I thought maybe that was a problem last year and put a venturi eyeball into deep end return and 3/4" on the shallow end return and have been playing around with them. When I add 1 it increases pump pressure about 3/4 lb and the second one increases pump pressure about 2 more lbs so I am not sure that is good for the system but it really causes a good counterclockwise rotation of the water and they were on when I discovered this new outbreak. So I am just looking for reasons so I do not continually go through this.
