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# FAQ: How can I calculate how much Safe to use if I know exactly how much chlorine, chloramine or ammonia is present in my water?

In some situations one may be aware of their exact chloramine or chlorine levels and will wish to precisely tailor the amount of Safe used. This information is provided as is and it is assumed one is sufficiently adept at the mathematics to do the proper calculations in order to determine the amount of Safe needed for a given concentration of chloramine, chorine or ammonia.

The standard dose of 100 mg/100 L of water will remove 1 mg/L (ppm) of chloramine, 1.4 mg/L (ppm) of chlorine and 0.33 mg/L (ppm) of ammonia.
A general formula that should help to determine the amount to use in mg for a given chloramine level is

x = L*c where x = amount to use in mg, L = volume of water (tank volume if added to tank, or source volume if water change water), c = chloramine level in mg/L (ppm). So a 500 L tank with 2.5 mg/L of chloramine would require 500 * 2.5 = 1,250 mg or 1.25 g of Safe,

for gallons the formula is

x = 4*G*c (where G = gallons and 4 is a constant)

for chlorine it would be

x = 0.7*L*n where x = amount to use in mg, L = volume of water (tank volume if added to tank, or source volume if water change water). n = chlorine level in mg/L (ppm). So a 500 L tank with 2.5 mg/L of chlorine would require 500 * 2.5 * 0.7 = 875 mg, for gallons the formula is

x = 2.8*G*n (where G=gallons and 2.8 is a constant)

for ammonia it would be

x = 3*L*a where x = amount to use in mg, L = volume of water (tank volume if added to tank, or source volume if water change water). a = ammonia level in mg/L (ppm). So a 500 L tank with 2.5 mg/L of ammonia would require 500 * 2.5 * 3 = 3750 or 3.75 g for gallons the formula is

x = 12*G*n (where G=gallons and 12 is a constant)