I have a 30,000 gallon outdoor in ground pool with an auto cover, Frog chlorine system, heater and DE filter. Things have been going well up until last week.
Chemistry had been fine as far as I know. I do not have the recommended test kit I read about here, but am using a Taylor K1004 which uses DPD reagent, so maybe I can muddle through while I order another kit? But based on my testing confirmed by the evil pool store people who apparently don't know much except how to suck money out of my wallet was as follows.
We had some very heavy rain overnight. Kids had left something plugged in outside, and when it got wet, it tripped the GFCI which included the cover pump. With the cover pump not running, the pool cover filled with water and flooded. Saw it in the morning, reset GFCI, got cover pumped dry. Did not think to look at the pool at the time. Weather was cool all week, nobody swimming, did not check chemistry all week. I guess I should have, but honestly, I have left it alone for several days before, and as long as the FC was good at the start, it was fine after a few days. The worst thing I have had happen was the FC get to zero and a light algae get started. And I was always able to kill it quickly with a good shock. Well, that all changed this time. Next time I opened the cover, the water smelled BAD, there was an oily film on the water surface, and it was terribly cloudy - If I stuck my arm in to my elbow, I could not see my hand. It seemed to be "white" cloudy - no green tint. Also, the liner surface did not feel slimy, so it did not seem like algae was the issue. All the chemistry seemed the same, except no FC. I did not check CC. The only thing unusual was that the DE pressure was way high, and as a result, the circulation was minimal. I am guessing the rain water dirtied up the pool and clogged the filter, and I did not notice. So for a week, there was little or no circulation or filtration, and there was little or no chlorine addition occurring since the Frog depends on circulation to add chlorine. I went ahead and backflushed and recharged teh DE since that was obviously an issue. I also added a couple of pounds of granular I had in the skimmer since a zero FC was obviously not good.
Then I went to the evil pool store. Their results were the same as mine, and they checked CYA which they said was low at 10. They said I needed to add CYA and shock the pool and suggested granular and oxy. I added 4 pounds of stabilizer, 3 bags of oxy and 4 more pounds of granular in the evening. I have not ever tested chemistry after adding chemicals until at least 6 hours later, although maybe I should. When checking the next morning, the FC came up to maybe 3, no change to water appearance, then FC dropped right back off by the evening. That evening, I hit it with 8 more pounds of granular - same result the next morning - came up to maybe three, and no change to water. So I hit again with another 8 pounds. That evening, again, no real gain to FG and no improvement to water. So I really hit with 10 more pounds of granular and 5 gallons of 12% liquid I still had. By the next day, still no improvement. But by now the pH was low about 6.8 due to all the granular I had added. Note that for about 24 hours after the first DE backflush and starting to add granular in excess, the DE would build pressure and need flushed - the first time after maybe 4 hours, then six then 10. But for a couple of days now, the DE pressure has been steady like it is not accumulating anything.
I went to the pool store again. They confirmed my results and said the CYA was up to 40, maybe due to the CYA in the granular. They just said I needed to shock it more. I questioned how that was going to help since it had not helped until then. They ran a few more tests and said my phosphates (which I have read in here don't mean squat) were 1500 which is way high according to them. They also suggested that I use 12% liquid for any more shocking since my CYA was good and the granular was driving the pH down. And they suggested pH up to get that back in line. And after I pressed about what else could be wrong, they suggested treating the phosphates. All I have done since then is add the pH up to get the pH back to 7.3 which seems OK.
Note that throughout all of this, the appearance of the water has not changed AT ALL. The only thing that has really changed is that it stopped stinking after the first shock. But it is still totally cloudy.
Then I did some reading here. And I am thinking SLAM is the solution. But I have a few questions. In a 30,000 gallon pool, I understand a gallon of 12% liquid should get me about 4ppm of chlorine, and that a pound of granular is about the same as a gallon of 12%. So I would have expected that 6 pounds of granular would get me 24ppm. And 8 would get me 32. And 10 plus 5 gallons of 12% would get me 60. But I have not seen anywhere near those kinds of increases. Is it just because I am not checking frequently enough, and it is dropping back off by the time I am checking?? How long after adding liquid in front of the jest until it is dispersed and I can get a good read? I am thinking to hit it with the 12% liquid to get to 16ppm since my CYA is at 40, but I don't know if that should just mean 4 gallons at 4ppm gain per gallon, or if that means add and add and add and add until I see 16 (which I can not measure with my test kit, but thought I could dilute 4X or 5X to get in range???)? Or if something else is going on since I am not seeing the gains I would expect from the amounts I have added?
Despite the trash talk I have read on here about phosphate myths, should I actually be concerned if they say it is 1500?
I apologize for all the rambling, but I am trying to share what I have seen and what I am thinking. And I am sorry I do not have all the results and test kit yet. I will. But in the meantime, I am hoping to make some progress.
Thanks in advance for your generous and patient assistance.