Swimming Pool Chemical Dosing Converter

Understanding Pool Chemical Dosing

Proper chemical dosing keeps swimming pool water safe, clear, and comfortable. The amount of chemical needed depends directly on the pool volume. Underdosing leads to algae growth and unsafe water, while overdosing wastes chemicals and can irritate skin and eyes. All dosing starts with knowing your pool volume accurately.

Pool Volume Calculation:

Rectangular pool: Volume (gallons) = Length × Width × Average Depth × 7.48 Round pool: Volume (gallons) = π × Radius² × Average Depth × 7.48 Oval pool: Volume (gallons) = Length × Width × Average Depth × 5.9

To convert: 1 US gallon = 3.785 liters and 1 liter = 0.2642 US gallons

Chlorine Dosing (Sodium Hypochlorite, liquid bleach 12.5%):

To raise free chlorine by 1 ppm (part per million):

• 10,000 gallons needs approximately 10 fl oz (300 ml) of 12.5% liquid chlorine
• Per 1,000 gallons: about 1 fl oz (30 ml)

For granular chlorine (calcium hypochlorite, 65%):

• 10,000 gallons needs approximately 2 oz (57 g) to raise 1 ppm

Target Ranges:

pH Adjustment:

To lower pH by 0.1 (using muriatic acid, 31.45%):

• 10,000 gallons needs approximately 4 fl oz (120 ml)
• Per 1,000 gallons: about 0.4 fl oz (12 ml)

To raise pH by 0.1 (using soda ash / sodium carbonate):

• 10,000 gallons needs approximately 1 oz (28 g)

Total Alkalinity:

To raise alkalinity by 10 ppm (using sodium bicarbonate, ordinary baking soda):

• 10,000 gallons needs approximately 21 oz (600 g)

Alkalinity buffers the pH, so fix it before chasing the pH itself. A pool with alkalinity under 80 ppm will swing its pH around every time you add anything, and no amount of acid or soda ash will hold it steady until the buffer is back in range.

Algaecide (Quaternary Ammonium, 10%):

Weekly maintenance dose:

• 10,000 gallons needs 2-4 fl oz (60-120 ml)

Shock Treatment (Super-Chlorination):

Shock treatment raises chlorine to 10-30 ppm to kill algae and bacteria. Using calcium hypochlorite 65%:

• 10,000 gallons needs approximately 2 oz (57 g) per 1 ppm, so about 1.3 lb (580 g) for a 10 ppm increase
• Always shock at dusk or night, as sunlight destroys chlorine rapidly

You will see “1 lb per 10,000 gallons raises chlorine by 10 ppm” repeated all over the internet, and it is a rounding that lost a third of the dose along the way. Work it from the chemistry instead. 10,000 US gallons is 37,854 litres, 1 ppm means 1 mg per litre, so raising free chlorine by 1 ppm needs 37.9 g of available chlorine. A 65% product is only 65% available chlorine by weight, so you need 37.9 / 0.65 = 58 g of the granules, which is 2.05 oz. Ten of those is 1.28 lb, not 1 lb. One pound of 65% cal-hypo in 10,000 gallons actually gets you to about 7.8 ppm.

Safety Notes:

• Never mix different chemicals together. Always add chemicals to water, not water to chemicals
• Wait at least 15 minutes between adding different chemicals
• Run the pump for at least 1 hour after adding chemicals to ensure proper mixing
• Test water with a reliable kit at least twice per week during swimming season