e. Desirable Chlorine Levels. When you test for chlorine, it is important to test
for free available chlorine (FAC), not just total chlorine. Free available chlorine is
measured in milligrams per liter (mg/1). As mentioned previously, the amount of free
available chlorine required depends on the pH. When the pH is 7.2 to 7.6, the required
free available chlorine is 0.4 to 0.6 mg/1. When the pH is 7.8 to 8.4, the required free
available chlorine is 1.0 to 2.0 mg/1.
Amount of chlorine (Cl) required depends on pH
Cl--O.4 to 0.6 mg/l
Cl--l.0 to 2.0 mg/l
f. Sources of Chlorine. Chlorine for use in pool sanitation can be obtained as
a gas, solid, or liquid.
(1) Gas chlorine. Pure chlorine gas can be purchased directly in steel
cylinders. The chlorine is compressed into a liquid and reverts to its gaseous state as it
is released from the tank. The Army generally uses gas chlorine.
(2) Calcium hypochlorite, Ca (OCl2). Calcium hypochlorite is a white
granular compound, often sold in tablet form. It is 70 percent available chlorine by
weight, and remains stable if kept cool and dry.
(3) Sodium hypochlorite NaOCl. Sodium hypochlorite is a clear, slightly
yellow liquid solution and in commercial form is 12 to 15 percent available chlorine. The
liquid can be fed directly into the pool. It is not as stable as the dry compounds. It
should be stored in a cool, dark place, and should be used within 30 days.
Part 3. Swimming Pool Equipment.
Swimming pool equipment must be handled carefully so that it works
effectively and is not a safety hazard. The inspector must ensure that the
equipment is being handled and maintained correctly.
1-13. CHLORINE GAS CONTAINERS
a. Storing Chlorine Containers. Containers of chlorine gas must be handled
with care to prevent the escape of dangerous chlorine gas. Figure 1-5 shows a typical
chlorine gas container.