WHAT IS BACKFLOW TESTING?
The
backflow valve test is a state required annual test. Any resident
or commercial business that has a valve is on a registry at
their local water utility, and will receive a notice from that
utility when the test is required. The backflow valve is installed
where the building codes apply. Most all business have a valve
and residents where a pool or irrigation sprinkler is installed.
Backflow
Prevention
In 1997,
the Missouri Department of Natural Resources revised a drinking
water regulation
entitled
“Backflow Prevention.” This revised regulation places
certain responsibilities on water
suppliers
to ensure that customer facilities identified as actual or potential
backflow hazards
provide
the necessary protection to prevent contaminants from entering
the public water system.
What
is Backflow?
Backflow
is defined as the unwanted reversal of flow in a water distribution
system. Due to
changes
in the hydraulic pressure in a water distribution system or
a piping system inside a
customer’s
premises, backflow occurs on a regular basis.
The polluting
substance, usually a liquid, tends to enter the potable water
supply if the net force
acting upon
the liquid acts in the direction of the water supply. Therefore,
two factors are
essential
for backflow to occur. First, the normal direction of flow in
the distribution system must
be interrupted.
Second, there must be a link or connection between the potable
system and the
source of
contamination.
Backflow
only becomes a serious problem when there are cross connections
within the water
distributions
system.
Public
Health Significance of Cross Connections
A cross
connection is a physical link between a source of pollution
or contamination with a
potable
water supply.
Public health
specialists have long been aware of the threat to public health
posed by cross
connections.
Education is the most important factor in cross connection control.
No one would
intentionally
connect plumbing fixtures, equipment, etc. to their water supply
if they knew it would
contaminate
their drinking water. But it happens thousands of times a day.
Various
court decisions have held water suppliers responsible for the
delivery of safe water to
consumers.
But the safety of our drinking water supply can be jeopardized
at any location, at
any time
because of the frequency of plumbing defects and cross connections.
Due to frequent
changes
in piping systems, an effective cross connection control program,
including continued
surveillance
of the public water system, is necessary to prevent backflow
incidents.
Components
of an Effective Cross Connection Control Program
The first
step in preventing backflow incidents is enacting local rules
that grant the water
supplier
the authority to enforce the cross connection control program.
For the water supplier
to comply
with the state backflow prevention regulation, the local rules
should include the
following
provisions:
•
A requirement for annual testing of assemblies and inspection
of air-gaps.
•
Authority to enter customer premises for purposes of inspection.
•
Authority to terminate water service for failure to comply.
Another
responsibility of the water supplier is to notify customers,
where backflow hazards exist,
that they
must comply with the local rule. Once these customers have been
notified, the
supplier
must maintain records of inspections, exemptions, or installation
of assemblies.
A local
program may not be less stringent than state regulations. Local
plumbing codes may
require
additional backflow prevention devices.
Methods
of Backflow Prevention
The department’s
Public Drinking Water Branch maintains a list of backflow prevention
assemblies
approved by the Foundation for Cross Connection Control and
Hydraulic Research
at the University
of Southern California www.usc.edu/dept/fccchr/. The following
methods of
backflow
prevention meet the requirements of the state backflow prevention
rule.
Air-gap:
An air-gap is the most positive method of backflow protection.
It is a physical
separation
between the water supply and the customer’s internal piping
system. The
distance
for an air-gap must be at least two times the diameter of the
pipe. For example,
a two-inch
separation is required for a one-inch water supply pipe.
Reduced
Pressure Principle Assembly: A reduced pressure principle
assembly is the
highest
level of mechanical backflow protection. The reduced pressure
principle assembly
has a hydraulically
operated relief port located between two spring loaded check
valves. A
drop in
pressure from the supply or an increase in back pressure from
the customer’s facility
will cause
the check valves to close and the relief port to open, creating
an air-gap within the
assembly.
If either check valve becomes fouled by debris, the relief port
will also open. The
drawback
to using an reduced pressure principle assembly is that it will
lower the pressure
available
to the customer’s premises.
Double
Check Valve Assembly: The double check valve assembly is
designed for low
hazard protection
only. The double check valve assembly has two spring valves
that act
independently
to provide protection from back pressure and back siphonage.
The drawback
to double
check valve assemblies is that both check valves are susceptible
to fouling by
debris in
the water system, which hinders their function and allows backflow
to occur.
Testing/Inspection
Requirements
The function
of all backflow prevention devices must be reviewed annually.
Air-gaps may be
inspected
by the water supplier. A state-certified backflow prevention
assembly tester must
perform
the specific testing procedures required to verify the proper
function of reduced
pressure
principle assemblies and double check valve assemblies.
The Public
Drinking Water Branch maintains a list of certified backflow
prevention
assembly
testers.
Basics of
Backflow Prevention: Missouri | Regulation 10 CSR 60-11.010-.030,
1/2008, PUB000393
