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Ask Dr. Laundry

Ask Dr. Laundry

Cleaning an In-ground Pool

By Dr. Laundry October 19, 2011

Q:  I have an in-ground pool and was told that putting Clorox® Regular-Bleach in the water would help prevent algae during the winter. Is this true, and if so, how much would I need if my pool holds 33,000 gallons of water?

A: There’s a protocol when using Clorox® Regular-Bleach for swimming pool disinfection.  On an ongoing basis, if you super-chlorinate the pool with 100-200 oz. bleach per 10,000 gallons of water, in addition to regular chlorination, algae growth can be prevented. However, it depends on several factors including how much the pool is used, sun exposure, and water quality.  It sounds like from your question you are getting ready to close your pool for the season, and the pool will not be used.  In that case, I would add 5 gallons + 2 ½ cups Clorox® Regular-Bleach to your 33,000 gallon pool.

(Here’s the math, if you are curious:  33,000/10,000 x 200oz. = 660oz/8oz per cup = 82 ½ cups.  80 cups is 5 gallons, so total to add would be 5 gallons + 2 ½ cups)

This treatment can be repeated as needed to keep algae growth under control—I would observe the pool and look for any signs of growth before repeating the treatment.  Also, if you decide to use the pool after super-chlorinating, you should use a pool test kit to confirm that the ppm available chlorine in the pool is 3ppm or less.

Is anyone else getting ready to close their pools for the winter?