I Stupidly Put Baquacil in my Chlorine Pool!!

[JohnHillman]

This is my first post...

I have a 24' round above ground chlorine pool, sand filter, running well for three years or so. We went to close it for the season and found it had an algae problem. So I shocked the @#$% out of it and put some algaeside in the pool, circulated 24 hours, then put some hydro-floc in the pool, unplugged the filter and waited 24 hours to allow the algae to gather at the bottom, at which time I vacuumed the pool to waste a few times. The water is perfectly clear and the bottom is clean, ph and alkalinity were a bit low (so I added some sodium hydrogen carbonate until they looked good) but the Chlorine level has been really high (over 10ppm) for two weeks.

So enter my stupidity. I read somewhere that you can lower chlorine with hydrogen peroxide. So I found a left over gallon of Baquacil, from when we were running a Baquacil pool, and looked at the ingredients to find it is basically 27% hydrogen peroxide. Not really knowing how much to add, I added the entire gallon.

It basically wiped out all of the chlorine in my pool. The water is still perfectly clear, and the bottom is clean (thank god it didn't turn green). I don't have a dropper type pool test kit, I've been using test strips for years with decent results. I guess I should pick one up.

So...., do I now just keep adding chlorine until the level comes up? Is this a free chlorine issue, but I may still have "locked" chlorine in the pool? Anybody help me out here??

 

[JohnT]

I expect you used Baquacil shock rather than sanitizer.

 

[JohnHillman]

It was Baquacil Oxidizer.....27% Hydrogen Peroxide....any idea how much chlorine I'm going to need to add??? :?

 

[chem geek]

Welcome to TFP!

The rough rule-of-thumb is that an equal volume of 3% hydrogen peroxide dechlorinates 6% bleach. So one gallon of 27% hydrogen peroxide will dechlorinate 27/3 = 9 gallons of 6% bleach. If I assume your 24' diameter round pool is 4' (48") deep in water depth, then that's 13,500 gallons so 9 gallons of 6% bleach would be 41 ppm FC. So that's a worst case estimate of how much chlorine you would need. It shouldn't be that much since you shocked the pool so that FC amount (less what was used in killing algae) should be subtracted from the 41 ppm FC and what is left is how much chlorine you need before you start to hold FC.

In practice, just start adding chlorine until you get an FC reading, but don't be surprised if it takes gallons of bleach or chlorinating liquid to do so. The good news is that the chlorine and hydrogen peroxide react quickly so you can add a gallon or two, then wait for circulation (perhaps 30 minutes or maybe an hour), then test FC (use an OTO test kit in case you overshoot since you don't want to bleach out a DPD test), if zero FC then add more and repeat until you get an FC that holds for at least one hour.