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A cross connection is any arrangement of plumbing between a potable (drinkable) water supply and a non-potable (undrinkable) water supply through which contamination could backflow into the potable water supply. Backflow is the reversal of the normal direction of flow in the drinking water system that can occur when the pressure in the customer's plumbing system becomes greater than the pressure in the city's water mains. If this situation occurs, there is the potential for contamination to enter the drinking water system by back siphonage or back pressure through a cross connection if one exists in the customer's plumbing system.
The Safe Drinking Water Act (SDWA) which was enacted in 1974, amended in 1986 and again in 1996, places the responsibility for cross connection control on the local water supplier. On January 11, 1978 Water Supply Cross Connection Rules were adopted by reference into the administrative rules under Act 399, P.A. 1976, which is the Michigan Safe Drinking Water Act. In order to comply with that act, the City of Jackson adopted a local ordinance:
Sec. 27-44
It shall be the duty of the water department to cause inspections to be made of all properties served by the public water supply where cross connections with the public water supply is deemed possible. The frequency of inspections and reinspections based on potential health hazards involved shall be as established by the water department and as approved by the state department of public heath.
Based upon this responsibility, the City of Jackson Water Department has developed a Cross-Connection Control Program. This program involves inspecting commercial and industrial plumbing systems and testing backflow devices. It is not our intent to find fault, only to eliminate all possibilities of contamination from entering our potable water system.
Detailed Description of Back Flow
Back Flow Caused by Back Siphonage:
For the purpose of cross connection control, an inlet is defined as any point where water is discharged from the plumbing system. Examples are the end of a pipe, faucet or the end of a hose. Back siphonage can occur when the inlet is submerged or has the potential to be submerged below the maximum point of overflow in anything capable of containing a liquid including such things as floor drains and utility sinks. If water is running when the inlet is submerged and a negative pressure occurs in the drinking water system, the fluid it is submerged in will be pulled back into the drinking water system. This type of cross connection is called a
Submerged Inlet.
Examples of Submerged Inlets:
1. A water supply line with the inlet submerged in a plating tank
2. A hose submerge in a pail of soapy water
3. A chemical sprayer attached to the end of a hose
4. A water softener recharge line submerged in a floor drain
5. A water supply line to a lawn irrigation system.
The drinking water system can be protected from potential contamination from submerged inlets with the application of the following:
1. A sufficient air gap which is defined as being 2 times the inside pipe diameter above the maximum point of overflow.
2. Atmospheric vacuum breaker
3. Pressure type vacuum breaker
4. Barometric loop
Back Flow Caused by Back Pressure:
Back flow caused by back pressure can occur if a customer's plumbing is directly connected (cross connected) to any other system that can generate a pressure greater than the pressure on the drinking water system. If this situation occurs then any fluid in the customer's plumbing system (potential contamination) will be forced back into the drinking water system.
Examples of a direct cross connections:
1. A makeup water line connected to a boiler.
2. A water line connected to another water supply such as a private well.
The drinking water system can be protected from potential contamination caused by a back-pressure situation with the application of the following:
1. Complete separation of the two systems.
2. A reduced pressure zone backflow preventer (RPZ).
If you have any questions regarding the Cross Connection Program please call 788-4090 and ask for the Cross Connection Inspector.
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