Photo: Thebluewriter · CC BY-SA 4.0Living in Diamond Bar, CA: what to set up and who to call
The closest public drop-off to Diamond Bar is Olinda Alpha Landfill, 4 miles out; the town decides whether residents may use it. Spectrum is the only wired internet provider that reaches most of Diamond Bar.
I’m new in town
What to set up in Diamond Bar, and who provides it. Tap an answer for the details and where they come from.
Power, water and internet
Who to call to start service at a new address in Diamond Bar.
Power comes from Southern California Edison
Southern California Edison (Southern California Edison Co), an investor-owned utility, serves all of Diamond Bar. Its homes paid an average of 31.5¢ per kWh in 2025, about $149 a month (its average across California, for customers on its standard service). California lets you buy power from another supplier; 30% of Southern California Edison’s home customers do, and Southern California Edison still delivers it.
Service territory: HIFLD Electric Retail Service Territories (map dated Aug 2023). Prices and customers: EIA-861, 2025.
Water comes from Three Valleys Mwd water system
The Three Valleys Mwd water system supplies Diamond Bar: about 50% of residents live in its service area. About 50% of homes are outside any mapped community water system, most likely on private wells, which EPA doesn’t regulate. It draws surface water and serves 0 people in all.
No health-based violations reported to EPA in the five years to October 2026, like 78% of the 11,392 systems serving <=100 people.
The system’s full record: EPA ECHO report
EPA SDWIS via Envirofacts (violations pulled Oct 9, 2026) and ECHO (lead samples, 2026Q3); service area: EPA Community Water System Service Area Boundaries v3.0. Violations are counted by the start of their compliance period. CA1910041.
5 home internet providers serve Diamond Bar
99% of 15,027 addresses can get 100/20 Mbps; 39% can get fiber.
| Provider | Technology | Addresses | Fastest (Mbps) |
|---|---|---|---|
| Spectrum | Cable, Fiber | 99% | 1,000/35 |
| Frontier | Fiber, DSL | 43% | 7,000/7,000 |
| T-Mobile | Fixed wireless | 61% | 100/20 |
| AT&T | Fixed wireless | 52% | 25/3 |
| Verizon | Fixed wireless | 44% | 300/20 |
FCC National Broadband Map, as of December 2025. Availability as providers report it, not speeds people get.
The nearest public drop-off is 4 miles away
Pickup rules, the dump and recycling in Diamond Bar.
Olinda Alpha Landfill
This isn’t Diamond Bar’s own facility. Whether Diamond Bar residents may use it is the town’s rule: check ci.diamond-bar.ca.us.
OpenStreetMap, as of Oct 9, 2026. © OpenStreetMap contributors.
Where your child goes to school
Public school districts and the school path by grade.
Most of Diamond Bar (62%) is in Walnut Valley Unified School District; parts are in Pomona Unified School District (38%).
B+School gradeSee Schools →U.S. Department of Education, NCES Common Core of Data, 2024–25. Enrollment rules and registration are the district’s.
Town hall and registering to vote
Who to call, and how to register.
Election office: FVAP local election office directory, updated Sep 2025; jurisdictions: EAC EAVS 2024. Registration rules and links: vote.gov, updated Nov 18, 2024.
Diamond Bar spans 2 ZIP codes
ZIP codes where Diamond Bar residents live, with the share of the town in each.
| ZIP | Post office name | Share of Diamond Bar | ZIP’s residents in Diamond Bar |
|---|---|---|---|
| 91765 | Diamond Bar, CA | 84% | 100% |
| 91789 | Walnut, CA | 16% | 21% |
Census 2020 ZIP Code Tabulation Areas, by census block; post office names: GeoNames (CC BY 4.0). ZIPs created since 2020 are missing.
Getting around, the ER and the library
One line each; the subject pages have the rest.
ER: CMS hospital data. Library: IMLS Public Libraries Survey, FY2024.
Questions about living in Diamond Bar
Who supplies Diamond Bar’s drinking water, and has it had violations?
The Three Valleys Mwd water system (EPA ID CA1910041). It reported no health-based violations to EPA in the five years to October 2026; 78% of systems its size had none.
Who provides electricity in Diamond Bar?
Southern California Edison (Southern California Edison Co), an investor-owned utility. Its homes paid about 31.5¢ per kWh in 2025 (EIA).
What internet providers serve Diamond Bar?
Spectrum, Frontier, T-Mobile, AT&T, Verizon (FCC, as of December 2025).
What ZIP codes are in Diamond Bar?
91765 (84%), 91789 (16%), by share of residents. Census 2020 ZIP Code Tabulation Areas.
What school district is Diamond Bar in?
Walnut Valley Unified School District. Parts of the city are in Pomona Unified School District.
How do I register to vote in Diamond Bar?
In California you can register online until 15 days before Election Day, in person up to and including Election Day, or by mail (postmarked 15 days before). Elections here are run by the Los Angeles Registrar-Recorder County Clerk. Check your registration at voterstatus.sos.ca.gov.
Sources & dates
Every answer above names its source. Here they are with their dates.
- Water: EPA SDWIS (Envirofacts, pulled Oct 9, 2026), ECHO SDWA 2026Q3, EPA CWS Service Area Boundaries v3.0.
- Power: HIFLD Electric Retail Service Territories (map Aug 2023); EIA-861 final 2025.
- Trash: OpenStreetMap, Geofabrik extract of Oct 9, 2026. © OpenStreetMap contributors (ODbL).
- ZIP codes: Census 2020 ZCTA relationship files; GeoNames postal codes (CC BY 4.0).
- Schools: NCES Common Core of Data, 2024–25.
- Registration: vote.gov, updated Nov 18, 2024 (read Oct 10, 2026). Official sites and area codes: Wikidata.
- Election office: FVAP local election office directory (fetched Oct 10, 2026; each record dated), EAC EAVS 2024 jurisdictions; registration and lookup links from vote.gov’s state data, checked Oct 10, 2026.
- Internet: FCC National Broadband Map, as of December 2025.