For a plumbing emergency in Ontario, close the main shutoff, and if you smell gas, leave and call 911 and SoCalGas at 1-800-427-2200. Ontario Municipal Utilities Company supplies water citywide and runs the gravity sewer lines. For anything inside your property, call the number on this page to be connected with a local plumber in Ontario.

Is the problem mine or the City's?
Ontario Municipal Utilities Company (OMUC), the City's own utility, provides drinking water across Ontario and manages the gravity sewer lines, with wastewater treated by the Inland Empire Utilities Agency. If water is flowing in the street, the meter is leaking, or a sewer manhole is overflowing, contact OMUC; Utilities Customer Service is (909) 395-2050. If the leak is in your yard line, under the slab or inside the house, or only your drains are backing up, that work falls to a plumber. Exactly where OMUC's part of the service line ends can vary, so ask OMUC if the leak is right at the meter.
Does the age of my house matter?
It does. Ontario was founded in 1881 by the Chaffey brothers as a planned citrus colony, and the median home in the city was built in 1980. Older neighborhoods near downtown can have galvanized supply pipe and aging drain lines, while newer areas such as Ontario Ranch have modern plumbing that tends to fail in different ways: supply hoses, water heater fittings and valves rather than corroded pipe. A plumber will approach a 1950s bungalow and a new Ontario Ranch tract home quite differently.
Water hardness plays a part too. The City reports its own groundwater averaging 124 mg/L hardness, imported water averaging 91 mg/L, and purchased groundwater between 137 and 177 mg/L on average, so scale builds up in water heaters and valves over time.
What if a replacement is needed?
A burst line or a dead water heater can usually be made safe the same day, but a permanent replacement may require a permit from the City of Ontario Building Department, which takes applications electronically through its Citizen Portal. A plumber can tell you whether the job needs one. If your property has a backflow assembly, Ontario requires it to be tested at least annually by a City-approved tester, so a plumbing repair that disturbs it may call for a retest. After-hours calls usually cost more, so ask about pricing before work starts.
A local note
Ontario is a major logistics hub around Ontario International Airport and the I-10, SR-60 and I-15 corridors, and traffic can affect how long a plumber takes to reach you. Arrival time depends on the hour and the plumber's schedule, so none is promised.
Emergency Plumber questions in Ontario
Who do I call about a water main break or a leak in the street after hours?
Are older homes here more prone to plumbing emergencies?
Does an emergency repair still need a permit here?
Water seems to be running somewhere but I can't see a leak. Could it be under the slab?
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