Leak Detection and Repair in Cupertino, CA

A Homeowner’s Guide to Leak Detection and Repair in Cupertino

Two water companies, one rule at the meter

The City of Cupertino doesn’t sell water. Your meter, bill and leak help come from one of two companies:

Area (City service-finder map, October 2026)	Water company	Phone
Northeastern Cupertino	California Water Service, Los Altos Suburban district	(650) 917-0152, also after hours
Southeastern Cupertino	San Jose Water	(408) 279-7900
Western Cupertino (City-owned system, leased to 2036)	San Jose Water	(408) 279-7900

The rule is the same with both: the company owns and maintains its side, the owner everything past the meter. San Jose Water spells out the split: it owns the meter, the meter box and the outlet coupling, while the owner has the service line to the house and the house shutoff valve. A leak in the yard, under the slab or in a wall is a private repair. See water line replacement.

Finding a leak before anything is opened

Start at the meter with every fixture and the irrigation off. San Jose Water’s guide: note where the sweep hand sits, wait 15 to 20 minutes, and look again. Cal Water’s meters have a test hand that turns whenever water passes. If the hand moves, close the house shutoff:

• Meter stops: the leak is inside, often a toilet, water heater connection or a pipe in a wall or slab.
• Meter keeps moving: suspect the yard line between the meter and the house, or the irrigation.

San Jose Water also offers a free home water audit, and Valley Water mails a free Do-It-Yourself Water Wise indoor survey kit with toilet dye tablets. Valley Water cautions that some flow monitors clamp onto the meter and not every retailer allows them, so ask your water company before buying one.

When the meter says “leak” and nothing is visible, we use acoustic listening, thermal imaging and pressure testing to locate it. See leak detection.

San Jose Water’s smart meters and courtesy adjustment

San Jose Water began installing smart (AMI) meters in July 2024. Its June 2026 filing with the CPUC counted about 168,000 installed and about 74,000 customers who had received continuous-flow alerts for possible leaks; Valley Water’s March 2026 table showed the rollout 49% complete. Once your smart meter is in, the SJWater HUB portal (sjwaterHUB.com) shows daily use and lets you sign up for possible-leak notices and alerts for unplanned use.

After a repair, San Jose Water may grant a one-time courtesy adjustment if the account has been active at least 12 consecutive months and the repair is verified. Keep receipts for the work.

Cal Water customers: its leak pages require repairs within five business days of a Cal Water notice. They don’t describe a leak bill adjustment, so ask the Los Altos Suburban customer center.

Fairgrove’s Eichlers and other slab homes

The City’s Eichler Design Handbook (2001) covers Fairgrove, the R1e-zoned neighborhood bounded by Phil Lane, Tantau Avenue, Bollinger Road and Miller Avenue: 220 Eichler homes built in the early 1960s. It describes Eichlers as single-story homes on slab foundations, with radiant-heat floors among their innovations.

In a slab home, leak signs to watch for:

• a warm or damp patch on the floor;
• cracked tile or lifting flooring;
• the sound of running water with everything off;
• a meter that never stops.

We pinpoint the leak so the slab is opened once, in the right place, or the line is rerouted overhead instead. See slab leak repair.

Permits, hard water and older pipe

• Permits: repairing a leak in a pipe, valve or fixture generally doesn’t need a permit; replacing a defective concealed pipe counts as new work and does. Licensed contractors can get an instant permit for an interior whole-house repipe.
• Hard water: both companies blend groundwater with treated Valley Water. Their 2025 reports put groundwater hardness at 288 ppm (San Jose Water) and 305 ppm (Cal Water). Scale and corrosion wear on older pipe and fittings.
• Housing age: the City’s Housing Element reports that the largest share of Cupertino’s homes went up between 1960 and 1979. When pinhole leaks keep appearing in pipe of that age, see repiping.

Sources

City of Cupertino: Water (service-finder map) · Building Division FAQ · Instant permits · Eichler Design Handbook, Fairgrove (2001) · Housing Element Technical Report (2024). San Jose Water: Who’s responsible for what · Check for water loss · Billing concerns and water use · SJWater HUB · Advice Letter 629a, AMI (June 2026) · 2025 water quality report. California Water Service: Is Cal Water responsible for plumbing leaks? · What if I have a water leak? · High bills · 2025 water quality report, Los Altos Suburban. Valley Water: Understanding your water use. Checked October 2026.