Need help getting pool in shape so I can close it....

[chem geek]

Welcome to the pool forum!

You can use Borax to raise your pH. It will take about 250 ounces of Borax (about 3.3 boxes that are 76 ounces each) to raise the pH from 7.0 to 7.5, but you could just raise your pH to around 7.3 instead (using 167 ounces of Borax or about 2.2 boxes) since your liqud chlorine and high FC will raise the pH -- eventually when you are done battling the algae and the FC gets lowered the pH will drop as well back to your 7.3 (or thereabouts).

After adjusting the pH (to prevent your vinyl from getting hurt by the acidity), the top priority for you is to get rid of the algae and that means keeping your FC level up at shock level according to Ben's Best Guess CYA chart which means adding liquid chlorine or bleach to maintain an FC of 20. Do you have a FAS-DPD chlorine test kit so you can test such high chlorine levels? By maintaining this high FC, all of the algae will get killed. You need this high FC because your CYA is a bit on the high side at 65. It may take more than just the 3 days to kill all the algae. Also, you will need to vacuum up the dead algae and/or clean your pool filter which hopefully has been filtering it out.

Your use of 3" tablets in the chlorinator means you are using Tri-Chlor tablets and these not only add chlorine, but also add CYA to your pool so you should stop using them because you already have high CYA. Also, the Tri-Chlor tablets are very acidic which is why your pH got low. Just use liquid chlorine (chlorinating liquid from the pool store or unscented bleach from anywhere, whichever is cheaper "per % of chlorine"). You can use BleachCalc to calculate how much chlorine to add or just remember the rough rule that 1 gallon of liquid chlorine will add the "% of chlorine" amount of ppm in a 10,000 gallon pool. So one gallon of 6% bleach adds 6 ppm in a 10,000 gallon pool (and 2 ppm in a 30,000 gallon pool, etc.).

That's all you should worry about right now. Your TA is OK. Remember that the most important rule when battling algae is Patience, Patience, Patience. I'm fairly certain that your pool will be completely clear within a week or less. You'll know all the algae is dead when you don't see any more, the pool is clear, and the FC level doesn't drop overnight (it may drop in the day if the pool is exposed to sun).

[EDIT] If you have a PC, you can use Michael Smith's BleachCalc which you can get from this link. It won't calculate the amount of Borax to adjust pH, but it will give do most everything else. [END-EDIT]

Richard