Why Backflow Occurs 6

Water demand varies with the time of day, day of the week and the weeks of the year. Water demands are also associated with unforeseen usages such as water main breaks or water used for firefighting. Understanding the factors that affect water use will allow the public water system operators to understand how water use will affect the water pressure in the public water distribution system. The type of community that is served by the public water system plays a role in evaluating the pressure fluctuations within the distribution system. A residential community with no or very little industrial water use may not see pressure fluctuations throughout the day but may see pressure fluctuations during different months of the year. Those public water systems that have residential and industrial water use may see pressure fluctuations in some areas of the distribution system during of the day. In the morning and evening the water use is high and during the day when consumers are a work the demand is low in the residential area of the public water system service area. The water pressure and direction of flow in the distribution will change depending on where the need occur. Water will flow from the high pressure to the low pressure. If there is a fire, the water will flow to the area of the fire because that is the low-pressure area. If the water demand for the fire is high it will pull water for entire distribution system, storage tanks and possible pull water from service connections. As in the illustration above, there is an unapproved privately owned fire tank and because of the water demand needed for firefighting, the water in the fire tank is flowing into the distribution system, creating a cross-connection incident and public health threat.