Federal and State law require that water suppliers protect their water systems from contamination. State regulations exempt single family residences used solely for residential purposes from assembly requirements if there are no hazards present. However, residences used for other purposes or with non-potable water used on site, such as reclaimed water, as well as commercial and industrial customers, are required by City Ordinance #7-03-001-0015 and State Administrative Code rule R18-4-115 to install and maintain backflow prevention assemblies. (Copies of Ordinance #7-03-001-0015 are available in the Flagstaff City Clerk's office or from the City of Flagstaff's Industrial Waste Monitoring Section at (928) 213-2117). When a determination is made by the Industrial Waste Monitoring Section that the potable water system may be subject to contamination through backflow or backsiphonage, a backflow prevention assembly will be required. Flagstaff Industrial Waste Monitoring Section makes these decisions on a case by case basis. New facilities are required to install the backflow prevention assemblies in a hot box outside the building (unless it is for the fire riser and then it can go in the fire riser room with adequate drainage to the sanitary sewer) as close to the water meter as possible.