Module 6 — Shock Chlorination
51
Sodium Hypochlorite (5¼% & 12%,
liquid form) has a shelf life. Purchase
new stock and check for an expiry
date. Buy only as much as you need
for the procedure. 12% industrial
sodium hypochlorite and 70% high test
hypochlorite are available from:
•
Water treatment suppliers
•
Licensed water well contractors
•
Swimming pool maintenance
suppliers
•
Dairy equipment suppliers
•
Some hardware stores.
Table 1
Amount of Chlorine Required for a Chlorine Concentration of 200 PPM
3
See modified procedure for large diameter
wells on page 53.
4
To reduce the chlorine concentrations to 50
ppm, divide the above chlorine amounts by 4.
1
Domestic chlorine bleach should not have
additives or perfumes.
2
Since a dry chemical is being used, it should be
mixed with water to form a chlorine solution
before placing it in the well.
Calculate the amount of chlorine that is required, as shown in Table 1. Mix the chlorine
with the previously measured water to obtain a 200 ppm chlorine solution.
Calculating Amount of Chlorine Example
If your casing is 6 in. and you are using 12% industrial sodium hypochlorite, you will
require 0.018 L per ft. of water in the casing. If you have 100 ft. of water in the casing,
you will use 0.018 L x 100 ft. = 1.8 L of 12% chlorine.
Using Table 1, calculate the amount of chlorine you will need for your well.
Casing diameter_______ Chlorine strength_______
L needed per 1 ft. of water_______ x _______ ft. of water in casing = _______ L of chlorine.
Step 3
If your well is located in a pit, proper
safety precautions need to be taken
during the chlorination procedure.
It is best to use a licensed water
well contractor who has the proper
equipment and experience to do the
job safely. Well pits are no longer
legal to construct.
Caution: Chlorine is corrosive and
can even be deadly.
Casing
Diameter
Volume of Water Needed
5 1/4%
1
Domestic
Chlorine
Bleach
12%
Industrial
Sodium
Hypochlorite
2
70%
High
Test
Hypochlorite
Water needed per 1 ft. (30 cm)
of water in the casing
L needed
per 1 ft. (30
cm) of water
L needed
per 1 ft. (30
cm) of water
Dry weight2
per 1 ft. (30
cm) of water
(
in)
(
mm)
(
gal.)
(
L)
(
L)
(
L)
(
g)
4
(100)
1.1
5.0
.019
.008
1.44
6
(150)
2.4
10.9
.042
.018
3.12
8
(200)
4.2
19.1
.072
.032
5.46
24
(600)
3
extra 200 gal.
extra 1000 L
.340
.148
25.40
36
(900)
3
extra 200 gal.
extra 1000 L
.76
.34
57.20