How do you chlorinate your pool with a sand filter?

Yes, if the sand in the "sand filter" is dirty. Clean water from the pool passes over the dirty sand bed in the filter thus reducing the amount of chlorine in the water. If it is sand from the beach or surrounding landscape - the answer is also yes because it is adding contaminants to the pool water. Anything that comes in contact with the water reduces sanitizer levels including the sun, wind, humans, pets, ducks, dust, pollen, cosmetics, under arm deodorants and on and on.

Ken