DISINFECTING WATER IN A LYSTER BAG
Water is disinfected at the unit level by adding ampules of calcium hypochlorite,
which are provided in the chlorination kit, to the water in a Lyster bag or other suitable
container. The following procedures describe how water in a Lyster bag is treated to
obtain a five-ppm chlorine residual.
a. Clean and Hang Bag. Clean the bag (see paragraph 2-4c) and hang it by
the supporting ropes as illustrated in figure 2-2. The supports must be sturdy since the
bag weighs approximately 300 pounds when filled with water.
b. Fill Bag. Fill the bag with water to the 36-gallon mark (about four inches from
the top of the bag) with the cleanest water available.
c. Prepare Disinfecting Solution. Put the contents of at least three calcium
hypochlorite ampules into a canteen cup, add a small amount of water from the Lyster
bag, and stir with a mess kit spoon until a thick mixture results. Then fill the cup one-
half full of water and stir again.
d. Add Solution. Empty the prepared solution slowly into the bag. There is no
need to stir. You should never put foreign objects such as sticks into the water.
e. Cover and Flush. Cover the top of the bag and flush the faucets by running
a small quantity of the water through each of the faucets. The flushing prevents any
unchlorinated water from being trapped in the faucets and disinfects the insides of the
f. Wait Ten Minutes. Wait 10 minutes after adding the disinfecting solution.
Waiting 10 minutes gives the chlorine time to kill disease-causing organisms in the
g. Test Chlorine Residual. If a five-ppm chlorine residual is present after 10
minutes, then most or all of the disease-causing organisms have been killed. If there is
no chlorine residual present or it the chlorine residual is too low (not sufficient to prevent
the water from becoming recontaminated), more chlorine will be needed. The
procedures for testing chlorine residual are given below.
(1) Select the appropriate (number five) plastic tube from the three tubes
provided in the kit.
(2) Take one orthotolidine tablet from the vial in the kit, place the tablet in
the cap of the plastic testing tube, and crush the tablet with the bottom of the
Empty the crushed tablet into the five-ppm testing tube.