Algae is driving me nuts

[shadowman]

I have been battling algae since I uncovered the pool in May. Twice I have shocked, brushed, vacuumed, and sweated my way to crystal clear water. But every afternoon I would have yellowish brown deposits on the bottom. After the first attempt I put my solar blanket on and within a week had green stuff on the sides. I started over with shocking, etc. and now I am back to clear water but the yucky deposits are there every day. Todays numbers:

FC = 6
TC = 6
CC = 0
PH = 7.2
TA = 90
CYA = 80

I have been using trichlor pucks for the past three summers with BBB but I shut off my injector this year and went to total BBB. If this is mustard algae, I know shocking is the only way to go but with my CYA so high, I am afraid to damage my liner with too much chlorine. I have been vacuuming to waste every day and refilling but the CYA is going down very slow. I now have a Taylor K-2006C so at least I can measure it. Is the yellow-brown stuff dead? Why is it there every day? Where to from here?

[mbar]

You will never get rid of the algae until you take your chlorine up to the shock levels in the "best guess chart" and keep them there until the chlorine holds overnight. You will have to check the chlorine 3x a day and take it back to shock levels. You will not damage your liner at these levels that are compatable with your cya. The high cya combines with the chlorine and the chlorine is not as effective as it is when the cya is low. Here is the chart. The most important thing is to keep the chlorine consistant. Try not to let it drop during the day, and give it a dose late at night before you go to bed. Keep the pump running 24/7, and brush the pool everyday. Here is the chart:

Use the info in this chart to help you figure out what levels of chlorine you need to maintain in your pool based on the amount of CYA (cyanuric acid, also called stabilizer) that you have in your pool. (FC = free chlorine)

Stabilizer . . . . . . Min. FC . . . . Max FC . . . 'Shock' FC
=> 0 ppm . . . . . . . 1 ppm . . . . . 3 ppm . . . . 10 ppm
=> 10 - 20 ppm . . . . 2 ppm . . . . . 5 ppm . . . . 12 ppm
=> 30 - 50 ppm . . . . 3 ppm . . . . . 6 ppm . . . . 15 ppm
=> 60 - 90 ppm . . . . 5 ppm . . . . . 10 ppm . . .. 20 ppm
=> 100 - 200 ppm . . . 8 ppm . . . . . 15 ppm . . .. 25 ppm

As you can see the minimum your chlorine should be is 5ppms - you really need to get it up to 20 and keep it there until it holds overnight.

Feel free to ask any questions you have

[shadowman]

OK, I added 2.5 gals of 12.5% chlorine per bleach calculator. Diluted test shows it at 20-25 2hrs later. It is warm and sunny today so I will keep a close eye on it.

[shadowman]

Well, we left on a short vacation, leaving instructions with our son to test the water and report the results. The next day he said the chlorine was down to 10 and there was no brown stuff in the bottom. The chlorine held the next day and the bottom was clean. When we came home today it looked beautiful and I tested and the numbers were:

FC = 5
CC = 0
PH = 7.4
TA = 90
CYA = 80

I just went out to put the solar blanket back on and was shocked to see the yellowish brown stuff back in the shallow end. I am close to ordering several truckloads of dirt to fill this thing in. I guess it's back to shock levels. Any advice?

[mbar]

With your cya 5 is your minimum chlorine level. I would suggest you take it back to shock and keep there for a couple of days. When you hold the chlorine overnight, you can start to let it drift back down, but keep it at the high side of your chlorine level which will be 10ppms for a couple of weeks. This way any algae that is just starting will get killed off - if the chlorine levels are too low, it is easy for it to get a foothold again Give a good dose of high chlorine and get rid of it once and for all

[chem geek]

If this "yellowish-brown stuff" is yellow/mustard algae, then instead of a minimum FC level of 7.5% of the CYA level (which keeps away green algae), it takes a minimum FC level of 15% of the CYA level to keep this algae away. At a CYA of 80 ppm that's an FC level of 12 ppm to keep this algae away from being reintroduced.

Also, the shock level for yellow/mustard algae is higher than for green algae, but with such a high CYA level it's probably impractical. You should also make sure that the yellowish-brown stuff isn't dirt or pollen though it does sound like algae.

Richard