Plumber in San Dimas, CA: A Clear Permit List and Very Hard Water

San Dimas's permit list names more than most cities

The City of San Dimas's permit page lists plumbing work, water heaters whether replaced, relocated or new, and replacing water or sewer lines as work that needs a building permit. It lists irrigation systems, with a backflow preventer required. The only plumbing item it calls exempt is replacing washers and faucets.

The city's 2025 water heater handout says a plumbing permit is required for all water heater replacements or new installations within the city. A homeowner guide also lists re-piping and sink replacements as permit work.

Job	What the city says
Replacing washers or faucets	Exempt
Water heater, replaced or new	Permit
Replacing water or sewer lines	Permit
New or changed irrigation	Permit, backflow preventer required

Building and Safety answers project questions at 909.394.6260. Hours are Monday to Thursday, 7:30 a.m. to 5:30 p.m., and Friday, 7:30 a.m. to 4:30 p.m. The city's own handouts give two different phone numbers and street addresses, so use the permit page's number.

Golden State Water, and a number worth knowing

The City of San Dimas's resident guide says its water provider is Golden State Water. Golden State's 2025 report for the San Dimas system lists total hardness with an average of 205 mg/L and a range of 85 to 307. The U.S. Geological Survey classes anything above 180 mg/L as very hard.

The company runs a 24-hour customer service line at 1.800.999.4033 for service problems at the meter. A leak on your side is a plumber's job. The practical effect of the hardness is scale, which is why fixing a scaled-up water heater and treating hard water both come up here.

• Ask Golden State which part of the system serves your street.
• Size any softener from the report, not from a guess.
• Ask the plumber to flush the tank on a schedule.

Sewer: the County runs the mains, you own the lateral

The City of San Dimas says its sewers are maintained by the Los Angeles County Consolidated Sewer Maintenance District. Los Angeles County Public Works says sewer laterals are entirely owned by the private property owner they serve. The city's Public Works Department can be reached at (909) 394-6240.

So a backup has two possible owners. A camera shows which, and the plumber can mark the distance. When the failure is in the lateral, sewer lateral repair choices covers the options.

Irrigation work and the backflow preventer

The City of San Dimas lists irrigation systems on its permit page and notes that a backflow preventer is required. That matters if you are adding a sprinkler zone, moving a valve or replacing a section of buried line. A backflow preventer keeps irrigation water from flowing back into the drinking supply.

Ask the plumber or irrigation installer whether the work touches the line that feeds the system, whether a preventer is already in place and who tests it. A leaking irrigation valve can look like a plumbing leak on the meter, so shut the system off and repeat the meter test first.

• Ask whether the permit covers the irrigation change and the preventer.
• Ask where the preventer sits and whether it is accessible.
• Ask who tests it, and how often.

If the meter stops once irrigation is off, the leak is in the system and not in the house. That distinction saves a service call, and it tells the installer where to start.

Which ZIP is your address?

The city's own handouts use two ZIP codes for the same City Hall area, 91773 and 91723. Mailing ZIPs do not always match city lines. When you ask about a permit or a water account, give the street address and not only the ZIP.

When you call (833) 571-0120, the plumber will confirm service for your block.

Common calls from San Dimas homes

• Water on a ceiling: where leak tracing starts.
• Pipes that fail often: whole-house pipe replacement.
• A slab that is warm in spots: warm slab spots.
• Sink and faucet leaks: faucet repair checks.

San Dimas: a plain-language checklist for the plumber's visit

A visit goes better when you know what to expect. Before the plumber arrives, clear the area around the fixture or heater and make sure someone age eighteen or older will be home.

• Ask for an arrival window and a name when the visit is booked.
• Ask what the plumber will check first, and what that will tell you.
• Ask for the finding and the options in writing before any work starts.

A good plumber explains the finding in plain language and lets you decide. If the work needs a permit, ask who pulls it and who schedules the inspection.

San Dimas on the map

Boundaries between cities, unincorporated pockets and water districts sit close together here, so give the full street address when you call.