Plumber in Ontario, CA

Two very different Ontarios

Ontario has some of the oldest houses in the 909 and some of the newest. The Chaffey brothers founded it in 1882 as the Ontario Model Colony and laid out Euclid Avenue as its main street, and the city incorporated in 1891. A century later, the land that's now south Ontario was still dairy farms. Where your house sits in that timeline says a lot about what's inside your walls.

Central Ontario and the historic districts

The neighborhoods around downtown and along Euclid have homes going back to the early 1900s. Rosewood Court and Armsley Square were both developed in 1924 and are designated historic districts, with Period Revival houses in French, Tudor, Colonial Revival and Mediterranean styles. El Morado Court includes Craftsman bungalows. Houses this age may still have galvanized water pipe, cast iron drains and clay sewer laterals, often patched together with newer pipe from decades of repairs.

Postwar and 1980s growth

Ontario grew from about 23,000 people in 1950 to about 89,000 in 1980 and 133,000 by 1990. That's two big building booms: postwar tracts through the 1950s and 1960s, and another wave in the 1980s. Most of those homes are on slabs with copper water lines underneath, or galvanized in some of the earliest ones. The postwar copper is 60 years old or more, and slab leaks and pinhole leaks are common calls in these neighborhoods.

Ontario Ranch

South Ontario was part of the county's dairy preserve, once the biggest concentration of dairy cows in the country. Ontario annexed about 8,200 acres of it in 1999 and called it the New Model Colony, after the Chaffeys' original plan. Now known as Ontario Ranch, it's planned for tens of thousands of homes. Edenglen, the first neighborhood, opened in 2007 on the site of a former family dairy.

These homes are built to recent California codes, so you'll find low-flow fixtures, plastic drain lines that roots can't easily get into, and a better chance of a tankless or high-efficiency water heater. The plumbing calls are different here: water heaters and tankless units that have never been flushed, faucet cartridges and aerators clogged with scale, pressure regulators that need adjusting, and warranty questions on homes that are only a few years old.

Your water: Ontario Municipal Utilities Company

Ontario runs its own water utility, Ontario Municipal Utilities Company (OMUC). Its 2025 water quality report breaks the supply down like this:

• 64.5 percent local groundwater from city-owned wells.
• 27.7 percent groundwater purchased from the Chino Basin Desalter Authority and Jurupa Community Services District. The desalters treat Chino Basin groundwater to remove salts and nitrate.
• 7.8 percent from the Water Facilities Authority, which treats imported State Water Project water, and San Antonio Water Company.

Hardness depends on the source. Water from city wells averaged about 124 mg/L in 2025, imported water about 91, and the purchased groundwater sources between about 137 and 177. That's roughly 5 to 10 grains per gallon, moderately hard to hard, and enough to build sediment in a tank heater and scale in a tankless one over a few years. OMUC collected more than 25,600 water samples in 2025 for that report.

New home? Check the warranty first

If your Ontario Ranch home is only a few years old and something seems wrong with how it was built, like a leak at a fitting inside a wall or a drain with the wrong slope, start with your builder. Most new homes come with a builder warranty, and California law gives buyers a formal process for making construction defect claims. Clogs, worn parts and maintenance are a plumber call either way.

Permits in Ontario

Plumbing permits come from the City of Ontario Building Department. Plan check, permit status and inspection scheduling run through the city's Citizen Portal. Water heater replacements, repipes and sewer line replacements generally need a permit, and the licensed plumber normally pulls it.

Nearby

North of Ontario, Upland shares the Agua de Lejos treatment plant and the San Antonio Water Company. To the south and west, Chino has its own dairy-country history and some of the hardest well water in the area. To the northeast is Rancho Cucamonga.