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| New plumbing in residential and commercial buildings,
pipelines and distribution systems should be sanitized to kill
bacteria when first put on line, or if repairs or service has
been performed. Shock chlorination is one of the most popular
methods for sanitizing pipelines. Chlorine's powerful germicidal
action eliminates slime bacteria, molds and algae. |
| The threat of excessive microbial growth along
the interior walls of drinking water distribution pipes is a
major health concern of water distribution officials. Bio-fouling
-- the development of an organic bacterial community, also commonly
known as bio-film -- is composed of microorganisms and their
secretions. It is present in almost every water distribution
system, and when uncontrolled may present a threat to public
health. |
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| Bio-films are layers of bacteria that attach to the
interior walls of water distribution pipes and to one another -- most
heavily around corroded surfaces on pipes. The bacterial community
traps nutrients, microbes, and waterborne pathogens to eventually
form an almost impenetrable material. Almost immediately after attaching
itself to pipeline walls, the organism begins building upon itself,
adding layer upon layer, forming a plaque-like coating. |
| The start of bio-film growth can
begin when the pipeline or distribution system is new due to the presence
of dirt, foreign material, piping construction materials and bacteria
from workers and the environment introduced during the construction
phase. Additional contamination can occur if the piping is serviced
or repaired. |
| It is extremely important that when
a new pipeline or plumbing system is put in service or repaired, a
thorough sanitizing and cleaning of the piping is done. |
| Advantages of sanitizing with
shock-chlorination include: |
| • |
Inactivates disease bacteria |
| • |
Cleans piping and equipment of dirt and debris |
| • |
Helps to prevent against bio-film formation |
| Proper and effective shock-chlorination
procedure requires: |
| 1. |
A dosage of 50 to 200 ppm of free chlorine
evenly distributed through out the piping and fixtures |
| 2. |
Testing of the residual to verify that the levels
are present at the fixtures and hose bib or valves sections. |
| 3. |
Contact time with the piping, undisturbed for 12 hours |
| 4. |
Retesting of the chlorine residual after 12 hours |
| If the chlorine residual is
less than 10 ppm after 12 hours, repeat the entire procedure above.
If the beginning dose is 50 to 100 ppm and the remaining residual
after 12 hours is less than 10 ppm, this indicates severe bio-fouling
or large amounts of dirt or slime present. |
| NOTE:
Shock-chlorination using the “slug-in method”:
We don’t recommend this method, since it relies
on introducing a slug or large amount of chlorine (usually
powdered bleach or tablets) into one section of the pipeline,
and hoping that this concentrated dose will properly sanitize
the downstream sections. This
is unreliable, and does not introduce a consistent, evenly
distributed chlorine residual of 50 to 200 ppm throughout
the system. It allows diluted water with varying residual
levels of chlorine to flush through the system.
It also can create very high levels of corrosive chlorine
(over 500 ppm which can damage fixtures and corrode copper
and stainless steel. |
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|
| 2. Shock
Chlorination Procedure by High-Pressure Metering Pump Injection |
| Professional water treatment specialists and distribution
system operators typically use this method. The procedure leaving
the water system or pipeline under pressure and using a high pressure,
low-volume metering pump to inject a concentrated chlorine solution
while the water is flowing at a given flow rate. After a chlorine
residual of 50 to 100 ppm is detected at each faucet or fixture (using
a high-range chlorine test kit, not a pool or hot tub test kit) the
chlorine solution is allowed to remain in the pipes for 12 to 24 hours. |
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| Injecting chlorine into a pipeline,
on the customer side of the back-flow prevention check valves
using a metering pump. |
|
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| 1. |
Shut off the main line. Identify an outside hose
bib or other opening in the incoming piping, on the customer
side of the main valve. If a back-flow prevention valve is present,
these can be utilized, as there is typically a ¼”
FPT port available. If no hose bib or opening exists, install
a ¼” or ½” threaded opening into the
main line to use for injecting the chlorine solution. |
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Figure 1:
Typical metering pumps with adjustable speed and pump stroke
adjusting knobs. These adjusting knobs make it easy to meter
in 10% to 100% of pump output and adjust output of pump for
various applications. |
|
| 2. |
Hook up a metering pump to the line (in our example, a 24 gallon/day
output metering pump is used), using a injection check valve so the
water cannot back-feed into the metering pump.See Figure 2. If metering
pump has a different output, adjust speed of pump or solution strength.
In this procedure, a concentrated chlorine residual will be injected
while the pipes are under line pressure from the street or city-water
system, so a check valve is used on tubing leading to the piping,
to prevent the water from backing up into the metering pump. |
| 3. |
Make sure to use a metering pump that can develop pressures higher
than the line pressure you are injecting into. |
| 4. |
Determine flow rate. Open up the faucets hot and
cold and read the water meter to determine gallons per minute. |
| 5. |
Use the formula and example below to adjust the metering pump: |
| NEW! You can use
our Online Metering Pump Selector
on the left of this
page to calculate how many gallons/liters of bleach you
will use per day. |
| Example:
Compute metering pump setting to achieve 100 ppm applied chlorine
dosage in a water stream flowing at 5 gallons per minute, using
full strength household bleach: |
| 5 gpm x 100 ppm x 1440 (minutes/day) |
|
| 52,500 (ppm of laundry bleach) |
|
= |
13.7 gallons per day |
| Output of pump is 24 gallons per day. The example
above calls for 13.7 gallons a day output. |
| 13.7 gallons per day |
|
| 24.0 gallons per day |
|
= |
.57 or 57% Set metering pump speed to 57%, which is 13.7 gal/day |
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| 6. |
Run the water in the building, or at a
valve or hose bib downstream until the bleach solution has filled
all the pipes and a strong odor of chlorine is coming from the fixtures
or faucets, both hot and cold. For best results, test the water at
each fixture to verify that there is at least a 50 to 100 ppm chlorine
residual, using a DPD method test kit. |
| 7. |
Allow the water to sit for 12 hours. Retest
for chlorine residual. If the water contains less than 10 ppm of chlorine,
repeat entire procedure. The slime, scale, and odor-producing bacteria
will interact with the chlorine and reduce the amount of chlorine
residual in the piping. If it uses up all the chlorine, or the chlorine
residual is less than 10 ppm, then the procedure may need to be repeated. |
| 8. |
Flush the piping and fixtures well to flush out
scale and colored from water from the piping. Unscrew aerators and
fixtures to avoid these items becoming plugged with sediment that
may have been loosened in the chlorination process. |
| Caution: If the
shock-chlorination procedure is being done on an old pipeline, or
one that has accumulated scale or buildup, the procedure can loosen
up scale, iron deposits and other materials in the piping, which can
clog fixtures, appliances and valves in the piping system, causing
a lot of problems. Care should be taken when flushing the piping,
and all aerators removed to prevent clogging. In some extreme cases
of corroded piping, the piping could fail and start to leak after
this procedure. |
| Figure 2: Typical
metering pump and solution tank installation showing injection valve
in piping, using a LMI brand metering pump. |
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