Green Pool Water & High Alkalinity
by Jonie Keysser
(Nixa, Mo USA)
The cover on our pool got blown off with all the bad storms this winter. The pool is very green and the alkalinity was very high. Hardness 1000, chlorine 0, pH 8.4, alkalinity 240, cyanuric acid 0. I put 2 gallons of muratic acid in the pool tonight and am running the filter all night.
This is an above ground pool, and there is new sand in the filter. I was not sure what else to do. Normally the pool does not look bad when I take the cover off. I would really like some advice.
Thanks for the question Jonie
Normally I would tell a pool owner to first shock their pool, but in this case I'll make an exception. The pool hardness seems to be outrageously high. I would encourage you to get a Taylor FAS-DPD K-2006 pool test kit.
Water Testing Kit
You can also take a sample of your pool water to a local pool store for analysis. But we'll keep the hardness at 1000ppm. There's really no chemical that can remove hardness from pool water. The best and safest way to decrease it is to drain 1/3 - 1/2 of the water and refill with fresh.
In your case I would say drain up to 3/4 of the pool water if in fact the reading is up that high. Your pool's calcium hardness shouldn't exceed 250ppm. I think that's what you should do first because you're going to need to do it anyway. If you shock and/or add any chemicals to the pool, they will all be wasted when you do a partial drain.
Test your fill water as well. This way you'll know what's going into the pool. Example: If the fill water has low alkalinity, then the high alkalinity you already have will work it's way
down without needing to add any pool acid.
Here are some other posts that will help you:
Swimming Pool Algae Has Taken Over Our Pool....And Our Lives!
Green Swimming Pool Water In Above Ground Pool..Algae..Shock
Swimming Pool Algae & Opening A Pool..HELP!!
Help!! New Pool Owner And The Chemical Tests Are All Over The Place. What Should I Do?
First, remove as much debris from the pool as possible. You need to shock with Dichlor. This is a fast acting chlorine with a stabilizer (cyanuric acid/CYA) in it. For every 10ppm increase of chlorine with Dichlor, you'll add 9ppm of CYA. With Trichlor tabs, for every 10ppm of chlorine added, you'll increase the CYA by 6ppm.
Here are other links you need for chlorine and chlorine tabs:
Swimming Pool Chlorine
Pool Chlorine Tablets
Swimming Pool pH Levels
Green pool water/algae
Green Pool Water
Swimming Pool Algae
The above links have the charts you need to make the right chemical adjustments. Keep filtering 24/7 as the chlorine does it's job with the algae. It will turn a white-grayish color. Backwash once per day. You may need to manually dose your pool with chlorine to keep it above 10ppm.
After that, you can use the above links to make your adjustments to the pH and alkalinity. Try to add chemicals in the evening. Allow for 1 complete turnover of the water, normally 8 - 10hours, then retest, and make another adjustment. If the alkalinity is still high, it will take some time and patience to get it back down to 80 - 100ppm. 120ppm is acceptable, but try not to go any higher.
Hope this helps and let me know how it turns out for you. Have a great swimming season.