Figure 5-13. Calcium hypochlorite solution calibration chart.
(1) Base charge. Referring to the information under the chart, it can be
seen that the chart is based on 1/8 pounds calcium hypochlorite per gallon of water.
This is the strength of the base charge placed in the chemical solution tank and the
strength of the recharge solution added when the solution level drops to about 4 1/2
inches from the bottom of the tank.
(2) Rate of feed. The vertical scale on the chart is the SCALE READING
corresponding to the graduations on the feeder controls. The horizontal scale is
graduated in ppm and expresses parts of chemical introduced into a million parts of raw
water. The diagonal Iine, or curve, correlates a given dosage in ppm with a
corresponding scale reading in gallons of solution per 'hour (gal/hr). To determine the
scale reading for a desired dosage, read the calibration chart by locating the specified
ppm of chemical " on the horizontal scale; trace a vertical Iine up to meet the curve;
then trace a horizontal Iine to the left to the SCALE READING. For example, using
figure 5-13 determine the scale reading for an application of hypochlorite solution at a
strength of 7 ppm. (Note: This means seven parts of calcium hypochlorite--not
chlorine--per million parts of water.)