Dead algae, high PH, low Alkilinity

[cadamy]

This is our first season to have a pool, so please forgive my ignorance. It's a 27,000 gallon in ground pool that's 40 years old. We use cholorine and a sand filter.

My pool filter stopped working for two days, and during that time we had 100 degree heat and my pool formed lovely green algae. Two days ago I treated it with Algae control followed by shocking an hour later (following directions). Now I have lots of what I believe to be dead algae, and my PH is 8.4 (high) and my Alkalinity is around 40 (low) according to my home test.

I understand that I need to vacuum the dead algae while the pump is on waste (correct?), but do I try to treat the chemical issues (alkilinity and PH) now, or do I wait until the algae is completely gone? Thanks for any help you can give!

[chem geek]

You can lower the pH with acid now -- note that it won't take as much because the TA as low. I'd wait on increasing the TA until after you've vacuumed-to-waste the dead algae that has settled to the bottom. Then use baking soda to raise the TA. I suggest you read the Pool School to learn how to properly shock the pool, defeat algae, and maintain the appropriate FC level for your CYA level to prevent algae growth in the future (though without circulation when a pump dies, this becomes more difficult). You should also get a proper test kit if you don't already have either the Taylor K-2006 or the TFTestkits TF-100.

[no running by pool]

you should wait to adjust the PH and TA because if your still at chlorine shock level your chemical reads are bleached out and not correct. You have plenty of time to fix these readings so wait until evrything is back to normal without algae and chlorine level drops back down to normal and then see where PH & TA readings are at.

[cpo2go]

Go ahead and vacuum out the algae to waste if your filter has that option. You will lose water and need to re-fill pool up to the middle of the skimmer.

At that point, you will need to re-test anyway and make adjustments accordingly.