Protection of Rural Drinking Water Pipelines

The reduced pressure backflow prevention assembly provides the highest level of mechanical protection.

By T.J. Macaulay, Saskatchewan Health

Rural drinking water pipelines have benefitted those areas of the prairies where water shortages are experienced. However, this benefit does not come without the risk of contamination of the drinking water within the pipelines.

For the most part, contamination will result from cross-connections. A cross-connection exists when there is a physical connection between a drinking water supply line and a source of contamination or pollution.

Farmsteads that are connected to rural drinking water distribution lines usually also have private water supplies. Cross-connections become a problem when farmers interconnect the existing private water supply system with the rural water pipeline system.

The interconnection of private water systems with public systems is normally prohibited by plumbing regulations. However, in Saskatchewan, provincial authorities see the interconnection of the two systems as inevitable. Therefore, a great deal of effort has been expended educating those involved with the pipelines on the need to protect the systems.

Pipelines can become contaminated when an unprotected cross- connection exists and backflow caused by backpressure or back-siphonage occurs. Backpressure happens when the private system is under a higher pressure than the pipeline system, and back-siphonage can occur when a negative or reduced pressure exists in the pipeline system. There are a number of different methods that can be used to protect water systems from these problems. When choosing a protection method, the following degrees of hazard are to be considered:

• SEVERE: A CROSS CONNECTION INVOLVING ANY SUBSTANCE IN SUFFICIENT CONCENTRATION TO CAUSE DEATH, SPREAD DISEASE OR ILLNESS.
  
  
• MODERATE: A CROSS CONNECTION INVOLVING ANY SUBSTANCE WHICH HAS A LOW PROBABILITY OF BECOMING A NUISANCE OR BE AESTHETICALLY OBJECTIONABLE IF INTRODUCED INTO THE DOMESTIC WATER SUPPLY.
  
  
• MINOR: AN EXISTING CONNECTION BETWEEN THE DOMESTIC WATER PIPE AND ANY PIPE, VAT OR TANK INTENDED FOR CARRYING OR HOLDING DRINKING WATER, WHICH HAS A LOW PROBABILITY OF BECOMING A MODERATE HAZARD.

Backflow prevention methods range from an air gap to mechanical devices such as pressure vacuum breakers. When choosing a device, consideration should be given to the: rating for the degree of hazard; ability to test while in use (in line); compatibility within the system; availability of drainage for atmospheric ports; protection from tampering; and cost.

When considering a mechanical device, keep in mind that there is a need for an on-going testing and monitoring program to ensure that the devices are working and remain in place.

In Saskatchewan, assistance in choosing the proper device can be obtained by contacting your local public health inspector.