I have an in-ground plaster pool. It has been getting a slight film of brown-green algae on the walls and corners. I am having a difficult time getting to the crystal clear water I have had in the past.
I bought the house about 5 years ago, but this year I am having trouble maintaining the pool. Up until now, I have just been taking the water to the pool store every couple weeks. They gave me a print out, sold me some stuff, and I followed the dosing instructions. The irony is that I took a fair amount of chemistry in high school and college and have a fairly sophisticated coral reef aquarium, so I believe I have the technical background for maintaining a pool myself but until now I have not really brushed up on it. It was just one more thing to have to learn, and what I was doing seemed to be working, so I kept doing it. I added solar panels this year, so the temps are higher than previous years. This also means we use the pool more. I go to two different pool stores. Leslie's is closer, but the service there can be horrible. I also go to Aquarius in Walnut Creek, and they seem very knowledgeable, but are not open on Sundays and are farther away.
Here's some of the drama. After seeing some algae film last weekend, I went to Leslie's with a water sample. The guy at Leslie's told me my Chlorine was too high (yes high). My pH was also a little high, so he said I had plenty of Chlorine but at pH of 8.0, it would not work. I had added 2 lbs of granular Chlor Brite about 5 days before, so I guessed that could have been true. He also said I was probably not running my pump long enough. Bringing the pH down and running the pump almost 24 hours per day did clear up the pool a fair amount, but by this weekend, the pool had some algae again. I went to Aquarius on Sat, and they gave me the readings below, but my Chlorine was basically gone. They told me to bring down the pH (2 quarts of Muratic Acid) and then two hours later add 3 gallons of liquid chlorine. I only added 2 gallons, but this definitely helped a lot and the pool is better today, although not perfect. The pH was higher again today (8.2), after coming down yesterday, so I added 2 more quarts of acid today. pH still seems high, but I have no idea how reliable my test hit is.
Anyway, after all of this I spent some time on this site today. Assuming it is accurate, this site seems to have more knowledge than the stores. I order the TF-100 test kit so I can do the testing and dosing myself. I think I see my main issue. With my CYA over 150, I need a much higher level of chlorine. I find it somewhat surprising that neither of the two stores mentioned this Chlorine/CYA relationship, but if pool store information is anything like local fish store information, I should not be surprised. Using the www.poolcalculator.com, it says I need to change out 75% of the water volume to reduce the CYA concentration. This will cost me $800+ dollars.
So, finally, my questions:
- Do I really need to reduce my CYA? (I assume the TF-100 test will help me get an accurate value here)
- I don't see any Mobile RO units in the San Fran Bay Area online, does anyone know of one?
- If I need to drain the pool,
- Is it safe to drain 75% of the water, or can emptying the pool cause it to crack?
- Is there a DIY on how to do this that is safe for an in-ground plaster pool?
Type: In-ground, plaster
Dimensions: roughly rectangular, 30'x14' with a 3' shallow end and 8' deep end
Volume: I use 18,000 gallons for my calculations
Temp: 82-90F (depends on outside temp and sun)
Filtration: 2100 rpm from 7am to 7pm (24 hours lately)
Intelliflow VS 3050 pump
Pentair Clean and Clear Cartridge (200),
Chlor Brite Sodium-Dichloro-s-Triazinetrione-Dihydrate (99%)Ganular
4x 3" Jumbo Tabs Trichloro-s-triazinetrione (99%)
Just switched to Liquid Chlorine yesterday.
Sun: Fully in the sun from 11am to 5pm in mid summer
Chemistry (From Lamotte WaterLink Spin Lab):
Free Chlorine: 0.55 ppm
Total Chlorine: 0.55 ppm
Combined Chlorine: 0 ppm
Hardness: 250 ppm
Alkalinity (w/stabilizer correction): 97.7 ppm
CYA: 151+ ppm
Copper: 0 ppm
Iron: 0.1 ppm
Borate: 7 ppm