My pool (specs in my signature) is about 2.5 years old. I live in South Florida. I maintained it myself for the first two years and have had crystal clear water the majority of the time. I had a few algae issues a long time ago. One was due to phosphates and the other was due to my ozonator dying. These happened a long time ago and I was able to get them under control easily. I used to run my pump 8 hours a day, during the day, and kept my chlorine generator low (around 25%). During the first 2 years, I hardly ever brushed my pool due to having the robot. I run the robot weekly.
At the end of last year, I had an issue where my robot pool cleaner wasn't working properly and my salt cell was having issues. I did not realize I had an issue due to a solar cover being on my pool. When I finally realized I had a problem, the water was very cloudy (white). Since then, I have tried many times to shock the pool and it seems like it works and then my problems begin again. I have done quite a bit of research on your site regarding testing and shocking.
The water has been clear for a couple of weeks, but I have to add significant amounts (up to a gallon) of chlorine daily to keep the chlorine level above 5 ppm. I even drained half of my pool water about a month ago. I now run my pump 12 hours a day and keep the chlorine generator at 100%. It can't keep up. Sometimes bubbles form on the surface of the pool if you splash the water. I have not used any form of algacide in over a year. I am cleaning my filter cartridge at least weekly.
Here are my current levels (Taylor K-2006 test kit):
FC - 27 (currently shocking, see below)
CC - 0
CYA - 50 (I added approx. 1 pound of stabilizer yesterday after taking this reading)
PH - 7.8
Alk - 110
CH - 120 (this was close to 400 the last time I tested. Maybe the partial refill dropped this?)
Ammonia - 0
I couldn't take it anymore and decided to try shocking the pool again. I decided to try and keep it in the 28-30 ppm range based on the CYA/Chlorine chart. The water has been crystal clear since I started, but the chlorine levels swing all over the place. It will look like it is stabilizing and then it will drop big time. My SWG is off during the time period below.
Here are my FC readings starting on Sunday (SWG turned off):
3:30 pm - 8 ppm, added 2 gallons chlorine
7:30 pm - 28 ppm, added 1/2 gallon chlorine
10:40 pm - 29 - 30 ppm
8:00 am - 22 ppm, added 1 large jug ultra bleach
9:50 am - 27 ppm
10:50 am - 27 ppm
12:30 pm - 26 ppm, added 4 cups chlorine
7:30 pm - 19 ppm, added almost full large bottle of ultra bleach
10:20 pm - 25-26 ppm
4/2 (I ran my fountains all day this day and overnight until the next morning)
7:50 am - 24-25 ppm, added 8 cups chlorine
11:00 am - 24 ppm, added 1/2 gallon chlorine
2:10 pm - 28-29 ppm, added approx. 1 pound of CYA
5:00 pm - 21 ppm (this is where I lost it and added 2.5 gallons of chlorine)
6:20 pm - 54-55 ppm
7:20 pm - 54-55 ppm
9:00 pm - 53 ppm
7:30 am - 35-36 ppm
1:00 pm - 34-35 ppm, added 2 cups acid (I do this every week at the same time)
3:30 pm - 27 ppm (getting ready to add yet more chlorine)
CC was zero during this whole time. I also checked ammonia and it was zero. Is this a normal type of fluctuation while trying to shock? I am going to go through a ton of chlorine at this rate. Keep in mind that my pool is crystal clear with no visible signs of algae. I brush it daily.
One other thing that I will mention is that my pool seems like it is having trouble holding CYA. We are hardly using the pool and it hasn't overflowed in more than 6 months, so it shouldn't be dropping. It just seems to want to stay at or below 50 ppm. I know ammonia can eat up CYA, but I have tested ammonia many times and have not seen a reading above zero. I am also trying a product (past 3 weeks) called AquaFinesse. A friend of mine is in the pool industry and gave me some free to try when he overheard me *****ing about my pool problems. I just wanted to make sure I am clear about everything I am using. Oh yeah, I have two filters that I rotate and they are both less than 6 months old.
Sorry for the long post. I am just trying to provide as much information as possible. Any help is greatly appreciated.