Commercial Plumbing in Ontario, CA

Does our building need a backflow assembly, and how is it tested?

OMUC's Water Quality Programs Division makes that call property by property. Once an assembly is required, the owner or customer has to have it tested at least annually by a certified tester the City has approved. Results are submitted electronically through the City's tester portal, and paper reports aren't accepted. A failed assembly has to be repaired or replaced within 30 days and then retested. Questions go to backflow@ontarioca.gov or (909) 395-2678. For warehouses near Ontario International Airport, restaurants around Ontario Mills and newer buildings in Ontario Ranch, that yearly cycle tends to be the most predictable plumbing obligation on the calendar.

What does Ontario's water do to commercial equipment?

The supply is mostly Chino Basin groundwater from City wells, plus purchased groundwater from the Chino Basin Desalter Authority and Jurupa CSD and imported State Water Project water treated at the Water Facilities Authority plant. The 2025 report lists hardness averaging 124 mg/L in City groundwater, 91 mg/L in imported water and 137 to 177 mg/L in purchased groundwater, so scale builds at different rates depending on the blend. The disinfectant residual includes chloramines as well as free chlorine, which is worth knowing for aquariums, labs or medical equipment that needs treated water. OMUC's inventory confirmed there are no lead service lines in its system.

Who handles the sewer and the permits?

OMUC maintains the City's gravity sewer lines, and IEUA treats the wastewater. Grease, wipes and paper towels from restaurants and multi-tenant buildings are the usual reasons a private line backs up before the flow ever reaches the main. Plumbing permits come from the City of Ontario Building Department at 303 East B Street, with applications submitted electronically through the Citizen Portal Access site.

A note on scheduling

Ontario was founded in 1881 as a planned irrigation colony and is now a logistics hub, and many businesses here run around shipping windows or long retail hours. Tell the plumber when water can be shut off and whether a failed test has a 30-day clock running, so the work can be planned around both. In multi-tenant buildings, post notice for every suite on the affected line.