Black Pool Water

[waterbear]

No, you don't have to drain but you WILL go through a lot of chlorine to oxidize any residual biguanide in the water. Even if your biguanide level was testing at 0 you stll need a lot of chlorine to complete the conversion, you can't just shock it once. You will also have to replace your filter sand if you have a sand filter or get a new cartrige if you have a cartridge filter once the conversion is complete. If you have a DE filter you will have to break it down and clean it, not just backwash it.

[Watermom]

And, to add to what Evan said, the more often you add bleach and maintain the high level of chlorine, the faster your conversion will go.

[pminct]

I understand replacing the sand in the filter - no problem.

How much/how often do you think I will need to shock to get rid of residual Baquacil?

How early should I start this if I want my pool open and swimable by Memorial Day, even though it will be much too cold for me to swim (but not too cold for kids to have their annual Memorial Day swim!!!)?

Patty in CT

[waterbear]

You need to raise your free chlorine to 15 ppm (or slightly higher) and KEEP IT THERE by testing at least 2 times a day (more will be better) untill your free chlorine is holding overnight. Your chlorine will not hold until all the biguanide is oxidized.