I am having a hard time maintaining chlorine levels. We went on vacation for 3 weeks and left my neighbor teenage boy in charge. Specifically asked to use bleach, every other day add a gallon. If it rained, add more, etc... Unfortunately, we had a week of tremendous heat and a second week of rain all week (perfect storm for algae)! Pool got B.A.D, according to teenager. He shocked it, according to pool store instructions (Booooo... he didn't understand that we DON'T use pool chemicals)... anyway, he tried. Pool was close to OK when we got back, just a little cloudy, nothing major. I've been trying to get it back to normal but I am not able to maintain chlorine levels. Also, PH has been higher (8.2), so I added the Muriatic Acid. Dropped it to 8.4.
Now, since I've been back, I have been using my new FT100 test kit and the 3 times I tried, I got a VERY high CYA result (90+). I lost sight of the black dot almost immediately after adding the mix. However, when I take the water to Leslie's Pool, they always come back saying the CYA is fine (at 70). I asked them specifically to pay close attention to that CYA test and they checked twice (on the three different occasions that I went)... so I wonder what is going on with such different results... My questions are:
1. Is high CYA responsible for loss of chlorine?
2. Where is the CYA results most likely mistaken? My testing with FT100 or Pool store?
3. Does Muriatic Acid go bad after a while? Last year I purchase a 6-pack and I still had 4 gallons left, so that is the MA I used last week to get the PH lowered.
4. Anything else I might be missing to get this stable?
5. Can shocking (with bleach) bring the PH up high?
6. Oh, husband is wondering, does CYA evaporate with normal water evaporation? It has been so hot that we have probably lost about 1 foot of water (1/6 the size of our pool). I figured no, because the CYA wouldn't evaporate with the H2O... he thinks it might, so why is the CYA still so high (if it is), why hasn't it gone down at least a little.
Oh, last night I added a gallon of chlorine, this morning CC was 0, I shocked it (with Bleach) because I saw some yellow starting to form on the walls, added 4 gallons bringing the CC up to 27 this evening. Unfortunately it may have raised the PH (although I find it harder to read the PH at night, since it is hard to distinguish between different shades of bright pink with low light.
CYA: (FT100 results 90+)
CH: Totally forgot to check for this one tonight.
Pool size: 13000 gallons/white plaster/ozonator with chlorine
THANKS IN ADVANCE FOR THE HELP!! I hadn't had any trouble for one year, and then I dared go on vacation!!! =D