Tankless Water Heater in Ontario, CA

How hard is Ontario's water on a tankless heater?

Moderately, and it depends on the source. Ontario Municipal Utilities Company draws mostly on Chino Basin groundwater from City wells, adds purchased groundwater from the Chino Basin Desalter Authority and Jurupa Community Services District, and blends in imported State Water Project water treated at the Water Facilities Authority plant. Its 2025 Consumer Confidence Report lists City groundwater at an average of 124 mg/L (range 82 to 150), imported water at 91 mg/L and purchased groundwater at 137 to 177 mg/L. Scale forms faster where water is heated, so plan on a yearly flush and consider a scale cartridge if you want extra protection. OMUC also confirmed there are no lead service lines in its system.

Will an older Ontario house need extra work?

Often, yes. Ontario was founded in 1881 as a planned citrus colony, and its median home was built around 1980. Houses near downtown and in the older tracts commonly keep the water heater in a garage or closet with a shared flue and a gas branch sized for a tank. A gas tankless unit needs its own sealed vent and a gas line that can feed a much larger burner, so the plumber measures both before naming a model. The newer homes in Ontario Ranch usually have garage layouts that make a sidewall vent simple, so the work there tends to center on gas sizing and unit choice.

Is a permit needed, and how is it filed?

Yes. The City of Ontario Building Department issues building permits, and applications are filed electronically through the City's Citizen Portal Access website. The department is at 303 East B Street, 909.395.2023. A tankless conversion involves the gas line, venting and water connections, so it is inspected. The installing plumber generally takes care of the application and meets the inspector.

One Ontario note

SoCalGas supplies natural gas in Ontario. If you smell gas near the heater or anywhere in the home, leave the building first, then call 911 and SoCalGas at 1-800-427-2200 from outside. Don't relight anything or use switches on the way out. A plumber can repair or replace gas piping to the heater once SoCalGas has made the area safe.