Chlorine Amounts Necessary for Disinfection


The table below addresses the quantities of chlorine needed to disinfect tanks and reservoirs, but it can be generalized and adapted to standard residential situations. Regular supermarket grade bleach contains 5.25% chlorine. Basic chlorine pellets used in dry pellet chlorinators are around 70% to 75% calcium hypochlorite.

Example of a practical application. To disinfect your 50 gallon hot water heater requires 1.5 cups of bleach left in the tank for two hours or 3/4 cup of bleach left overnight. For a 30 gallon tank, cut the amount in half. Keep in mind that a bit too much usually doesn't hurt anything. A plumber we know regularly uses a gallon of bleach for a standard hot water heater.

AMOUNT OF CHLORINE NECESSARY FOR DOSAGE AND TIME COMBINATIONS

Volume of Box, Basin, Reservoir or Cistern

5.25% Sodium Hypochlorite (Bleach)

65% Calcium Hypochlorite

100 ppm* for 2 hours

50 ppm* for 8 hours

25 ppm* for 24 hours

100 ppm* for 2 hours

50 ppm* for 8 hours

25 ppm* for 24 hours

50 gal

1½ cups

3/4 cup

3/8 cup

- -

- -

- -

100 gal

3 cups

3/4 cup

- -

- -

- -

200 gal

6 cups

3 cups

1½ cups

- -

- -

- -

500 gal

1 gal

7½ cups

3 3/4 cups

9½ oz

- -

- -

1,000 gal

2 gals

1 gal

7½ cups

1 lb 3 oz

9½ oz

- -

2,000 gal

4 gals

2 gals

1 gal

2 lb 6 oz

1 lb 3 oz

9½ oz

5,000 gal

- -

5 gals

2½ gals

6 lbs

3 lbs

1 lb 8 oz

10,000 gal

- -

- -

5 gals

12 lbs

6 lbs

3 lbs

20,000 gal

- -

- -

- -

24 lbs

12 lbs

6 lbs

50,000 gal

- -

- -

- -

60 lbs

30 lbs

15 lbs

100,000 gal

- -

- -

- -

120 lbs

60 lbs

30 lbs

* ppm = parts per million

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