Chlorine Level for winter closing

[truepoolblues]

Moved from HERE

New pool owner here, going through our first close this winter. We are in Canada, so the pump and all equipment will be fully turned off, all lines will be blown out, and we expect to get several inches of ice on top of the pool. A pool company here told me the reason you take chlorine to zero is because algae can't grow in water that cold anyway and since chlorine is heavier than water it will sink to the bottom of the pool when you turn the pump off over winter, causing unnecessary wear on the vinyl/fibreglass surface. Plausible logic for letting chlorine drop to zero before closing?

 

[ajw22]

New pool owner here, going through our first close this winter. We are in Canada, so the pump and all equipment will be fully turned off, all lines will be blown out, and we expect to get several inches of ice on top of the pool. A pool company here told me the reason you take chlorine to zero is because algae can't grow in water that cold anyway and since chlorine is heavier than water it will sink to the bottom of the pool when you turn the pump off over winter, causing unnecessary wear on the vinyl/fibreglass surface. Plausible logic for letting chlorine drop to zero before closing?

That pool company person never studied chemistry. It shows the type of babble that so called professionals authoritatively spout.

Chlorine is a gas and not a solid that can sink to the bottom of the pool.

Active chlorine compounds come in two forms - hypochlorous acid (HOCl) and the hypochlorite ion (OCl-)

Chlorine needs to be bound to a solid like calcium, or CYA, or water to add it to your pool. Then the chlorine ions and HOCL get dispersed with the H2O.