Cross Connection Control Quiz

Hint

The contaminant enters the potable water system when the pressure of the polluted source exceeds the pressure of the potable source.

Hint

First, plumbing is frequently installed by persons who are unaware of the inherent dangers of cross-connections. Second, such connections are made as a simple matter of convenience without regard to the dangerous situation that might be created. And, third, they are made with reliance on inadequate protection such as a single valve or other mechanical device.

Hint

The sodium hydroxide is brought to the plant in liquid form in bulk tanker trucks and is transferred to a holding tank and then pumped into 55 gallon drums. When the water main broke, a truck driver was adding the water from the bottom of the tank truck instead of the top, and sodium hydroxide back-siphoned into the water main.

Hint

Water purging is the preferred method of purging over the use of carbon dioxide since it is more positive and will float out any sludge as well as any gas vapors. The “purging” consisted of hooking up a hose to one of the private fire hydrants located on the property and initiating flushing procedures.

Hint

Authorities stated that the problem occurred when a water main broke at the same time that a pest control service was filling a pesticide truck with water. The reduction in pressure caused the pesticide from inside the tank to be sucked into the building’s water main. The pesticide contaminated the potable water supply of the office building and neighborhood area.

Hint

The workman for the exterminator company left one end of a garden hose that was connected to an outside hose bibb tap in a barrel of diluted pesticide. During the water service interruption, the chlordane solution was back-siphoned from the barrel through the house and into the water mains.

Hint

No backflow protection on make-up supply line to a hot-water storage tank

Hint

Atmospheric pressure exerted on a pollutant liquid forcing it toward a potable water supply system that is under a vacuum

Hint

The rate of increase for water is 0.433 psi per foot of depth.

Hint

One of the common occurrences of dynamically reduced pipe pressures is found on the suction side of a pump.

Hint

In addition to the negative pressure or reversed force necessary to cause back-siphonage and backflow

Hint

There are six basic types of devices that can be used to correct cross-connections: air gaps, barometric loops, vacuum breakers—both atmospheric and pressure type, double check with intermediate atmospheric vent, double check valve assemblies, and reduced pressure principle devices.

Hint

These devices are essentially modified double check valves with an atmospheric vent capability placed between the two checks and designed such that this “zone” between the two checks is always kept at least two pounds less than the supply pressure. With this design criteria, the reduced pressure principle backflow preventer can provide protection against back-siphonage and backpressure when both the first and second checks become fouled.

Hint

Maximum protection is achieved against backsiphonage and backpressure conditions utilizing reduced pressure principle backflow preventers.

Hint

The pressure loss through the device may be expected to average between 10 and 20 psi within the normal range of operation, depending upon the size and flow rate of the device.

Hint

The request to shut down the water supply is therefore a necessary prerequisite to protect the customer as well as limit the liability of the tester.

Hint

Method 1
Utilizing the differential pressure gauge and not shutting off number 1 shut-off valve. Figure 41)

Method 2
Utilizing “Duplex Gauge” or individual bourdon gauges, requires closing number 1 shut-off. (Figure 42)

Hint

To assist the water purveyor in the total administration of a cross-connection control program requires that all public health officials, plumbing inspectors, building managers, plumbing installers, and maintenance men participate and share in the responsibility to protect the public health and safety of individuals from crossconnections and contamination or pollution of the public water supply system.

Hint

Cross-connection control survey work should only be performed by personnel knowledgeable about commercial and industrial potential cross-connections as well as general industrial uses for both potable and process water. If “containment” is the prime objective of the survey, then only sufficient time need be spent in the facility to determine the degree of hazard inherent within the facility or operation.

Hint

The Department strongly recommends that all new retrofit installations of reduced pressure principle devices and double check valve backflow preventers include the installation of strainers located immediately upstream of the backflow device.