First of all I'd like to thank everyone on here for such a really cool website that has already saved me a ton of money and allowed me to understand the chemistry of what is happening inside my pool. Thanks to all.
That being said, I am perplexed for the first time in the 2 years of owning my pool. We have a 20K plaster inground pool, College Station, Tx. Pool has an infloor cleaning system by AA that does pretty well except for a few corners that collect some sand and dirt. The spa overflow runs often as it is one of the "zones" on the infloor cleaner, and the water thus overflows from the spa down a rock river that connects it to the pool. I suspect it is this that causes my PH to drift up a bit, and I seem to have to add about a gallon of acid per week (in small doses) as well as adjust my TA up with baking soda occasionally. I also have an ozone system on the pool but I don't count on this thing to really do much other than just add a touch of insurance to things in case we lose track of things and forget to add some bleach. Typically, I have tried to keep the chlorine around 2 -3 PPM, and that takes usually around 1/3 gallon of 8.25% per day, more in the summer, less in winter. We don't shut down the pool in the winter as it is a major water "feature" right out the back door. Sorry, I ramble. I try to keep the water at the recommended trouble free settings, and I also use boron in the pool (Boric Acid) at 50 PPM. The pool is not salt, and generally gets pretty low use as it's just the 4 of us.
I travel (a LOT), and I do everything I can to try to keep things stable in the pool, but things do fluctuate a bit. Of course I know that everything is a moving target, but I really try to keep especially the PH and Chlorine spot on. I use the TF100 test kit weekly and check the PH/Chlor about every other day.
So, here is my issue. A few weeks ago we had a small pool party. The day before I checked things and our Chlorine had gone to zero. I had never seen this happen, but immediately brought it back up to about 4 or 5 (calculated, not tested). That same day I jumped in the pool and found some kind of slimy green stuff starting to grow on some rocks. I then brushed all the area that I could find. A few days later, I noticed the water just didn't seem to be as clear as I was used to. Short story long, I gradually moved to the process of slamming the pool. During this time, however, my combined chlorine initially was zero, but a few days later I got a reading of 0.5. That was when I started to do some more reading and realized I had a problem requiring to slam.
Now that I am in this process, my pool seems to just be devouring chlorine. I am trying to keep the Chlorine at 16+, but there have been periods where it has gotten down as low as 7 overnight, then I add it back up to the upper teens as quickly as I can. I am using liquid chlorine and going through about 2 or 3 gallons easily per day. The pool is crystal clear, but continues to eat chlorine. I am down to less than .5 CC now, but it is hard to discern the difference with the test, technically it is reading zero but the test sometimes has just a slight hue of pink to it with a single drop.
Here are the numbers that I am typically running with the pool, and my slam chlorine level I am trying to stay at 16+. I am giving these numbers as a range because that is the typical range they run in as I adjust the chemicals.
PH 7.2 to 7.5
TA 80 to 100
CH 275 to 300
Some other information. About a month ago I introduced 4 bottles of pro team "Metal Magic" remover as I thought perhaps I had some white scale on the plaster, but not sure that did anything except add some chemicals to the pool, could this perhaps added phosphates? A week after that I cleaned my Hayward 525 sq ft filter and found that the filter was pretty nasty, and had a bit of a funk to the smell. Lots of dirt, dead bugs, and some sand came out. I have since ordered new cartridges just in case, but hate to put those into the canister until I figure out what my current problem is. (If I have one??)
My chlorine loss overnight continues to be in excess of 5, but my pool is crystal clear, and CC is 0. I will continue to slam, and when I get home I will be cleaning the cartridge and checking all the rest of things for something wrong (maybe I sucked a dead animal in the floor cleaner and it' stuck in there or something, or there is some nastyness that needs to come out of those filters).
Anyway, how long is this going to take (Almost a week now), and is there a chance I screwed up with the Metal Magic and phosphates or something?? I am at a loss. never had any issues before, would love to hear from ya'll.
BTW, my local Walmart just started selling liquid chlorine at 10% in the pool section, $3.96 a gallon normally, but last week it was on rollback to $2.50. I'm gonna buy all I can store. Also, my next pool upgrade is going to be the (CHEM) system to monitor my pH and ORP through the Omnilogic panel, and I'm gonna try to use a pump to feed liquid chlorine automatically and a CO2 system to control the PH. That's gonna be another thread.