Pool chemical dosing calculator
Chlorine, acid and shock to add by volume.
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How it's calculated
Every dose scales with the water: the rules of thumb are per 10,000 gallons, so the pool volume divided by 10,000 multiplies everything. For chlorine, the product sets how much raises 1 ppm in 10,000 gallons (10.7 fl oz of 12.5% liquid, 2 oz of cal-hypo), and that is multiplied by the ppm you want to add. Shock is the same with a 10 ppm rise. Muriatic acid lowers pH by about 0.1 for each 8 fl oz per 10,000 gallons at normal alkalinity, and 1.5 lb of baking soda per 10,000 gallons raises alkalinity 10 ppm. Alkalinity affects how pH responds, so fix it first, add in halves, and retest.
What order should I add pool chemicals in?
Alkalinity first, since it stabilises pH; then pH; then chlorine. Never mix products together or add them at the same spot, and never add water to acid. Run the pump, wait at least an hour between chemicals, and retest before the next step.
How much shock does my pool need?
A normal shock raises free chlorine by about 10 ppm: for 20,000 gallons that is a little over a gallon and a half of 12.5% liquid chlorine or about 2.5 lb of cal-hypo. Green water or a strong chloramine smell can need two or three times that. Shock at dusk so the sun does not burn it off.
Why does my pH keep rising?
Low alkalinity lets pH swing; aeration from waterfalls, bubblers and splashing drives it up; and liquid chlorine and cal-hypo both nudge pH upward. Get alkalinity to 80–120 ppm first, then small regular acid doses hold pH where you want it. Trichlor tablets do the opposite and pull pH and alkalinity down over time.
Results are estimates for informational purposes only and are not financial, medical or legal advice.