Dilution calculation formulas

If some chemicals are to high, you may have to dilute the water
to reduce it. Calcium, cyanuric, TDS, etc.
Ex. If calcium is 400ppm and you want to reduce it to 200ppm.
Source water (to add) is 100ppm
PR = test reading of pool water, ppm
SR = test reading of source water, ppm
FR = final test reading you want to adjust to, ppm
must be between SR and PR.
PV = pool water volume
SV = source volume to add
% = percentage of water you'll have to drain

% (to drain) = (PR - FR) / (PR - SR)

.67 = (400 - 200) / (400 - 100)
You'll need to drain 2/3 (67%) of the pool.

% times pool volume, will give you the amount of
water you'll have to drain and source(new) water you'll
have to add.

You can use this formula to also increase ppm of chemical.