Backflow testing in California
9 utility lists · 552 companies · 506 testers on the 6 lists that count testers. Largest list: City of Escondido Utilities, Water Division (92 companies). Your utility decides which testers it accepts, so start from the utility that sent your notice.
Utility lists in California, ranked by companies on the list
| Rank in state | Utility list | Area | Companies | Testers | vs national median | National rank (by companies) |
|---|---|---|---|---|---|---|
| 1 | City of Escondido Utilities, Water Division | Escondido | 92 | Company-level list | 1.6× | 10 of 33 |
| 2 | Riverside Public Utilities | Riverside | 89 | Company-level list | 1.6× | 11 of 33 |
| 3 | Irvine Ranch Water District | Irvine | 82 | 114 | 1.4× | 12 of 33 |
| 3 | East Bay Municipal Utility District | Oakland | 82 | 89 | 1.4× | 12 of 33 |
| 5 | Beaumont-Cherry Valley Water District | Beaumont | 66 | 80 | 1.2× | 15 of 33 |
| 6 | City of Sacramento Dept of Utilities | Sacramento | 64 | 101 | 1.1× | 16 of 33 |
| 7 | City of Modesto Water Division | Modesto | 57 | 57 | 1× | 17 of 33 |
| 8 | Marin Water | Corte Madera | 32 | 65 | 0.6× | 26 of 33 |
| 9 | Diablo Water District | Oakley | 6 | Company-level list | 0.1× | 33 of 33 |
Computed from the 9 California utility lists above, as fetched 2026-11-04 (UTC). National median: 57 companies per list across the 33 utility lists we hold (n=33). National rank 1 = the list naming the most companies; equal counts share a rank. Testers: only lists that name each company's testers carry a count. Not in the company counts: 33 entries for an individual tester with no company named and 14 entries for companies named after a person; we count those but do not republish them.
How many testers each company has
| Utility list | Testers with a company | Companies | Testers per company | One-tester companies | Largest company (testers) | National rank (testers per company) |
|---|---|---|---|---|---|---|
| Marin Water | 61 | 32 | 1.9 | 18 (56%) | 11 | 3 of 13 |
| Irvine Ranch Water District | 108 | 82 | 1.3 | 68 (83%) | 5 | 7 of 13 |
| City of Sacramento Dept of Utilities | 83 | 64 | 1.3 | 54 (84%) | 6 | 8 of 13 |
| Beaumont-Cherry Valley Water District | 79 | 66 | 1.2 | 56 (85%) | 4 | 9 of 13 |
| East Bay Municipal Utility District | 83 | 82 | 1 | 81 (99%) | 2 | 11 of 13 |
| City of Modesto Water Division | 57 | 57 | 1 | 57 (100%) | 1 | 12 of 13 |
Computed from the 6 California utility lists above, as fetched 2026-11-04 (UTC). Median across the 13 tester-level lists we hold: 1.3 testers per company (n=13); rank 1 = most testers per company. Counts only: we never publish testers’ names.
How current each list is
| Utility list | Version as printed | Date and age | Fetched (UTC) | We re-check it every |
|---|---|---|---|---|
| Marin Water | “Revised Oct. 23, 2026” | 2026-10-23 (dated on the list), 12 days before we fetched it; 1 of 22 by recency | 2026-11-04 | 120 days |
| East Bay Municipal Utility District | “Printed 2026-10-05” | 2026-10-05 (dated on the list), 30 days before we fetched it; 3 of 22 by recency | 2026-11-04 | 365 days |
| Diablo Water District | “Effective September 21, 2026” | 2026-09-21 (dated on the list), 44 days before we fetched it; 6 of 22 by recency | 2026-11-04 | 365 days |
| Beaumont-Cherry Valley Water District | “Revised 2026-08-04” | 2026-08-04 (dated on the list), 92 days before we fetched it; 8 of 22 by recency · Old list | 2026-11-04 | 35 days |
| City of Escondido Utilities, Water Division | “directory as fetched (97 listings)” | Live directory: current on the day we read it, 2026-11-04 | 2026-11-04 | 365 days |
| Irvine Ranch Water District | “5_18_26” | The list prints no full date; see the version as printed | 2026-11-04 | 365 days |
| City of Modesto Water Division | “directory as fetched (57 listings)” | Live directory: current on the day we read it, 2026-11-04 | 2026-11-04 | 365 days |
| Riverside Public Utilities | “6.1.26” | The list prints no full date; see the version as printed | 2026-11-04 | 365 days |
| City of Sacramento Dept of Utilities | “7.2026” | The list prints no full date; see the version as printed | 2026-11-04 | 180 days |
Computed from the 9 California utility lists above, as fetched 2026-11-04 (UTC). Median age at fetch across the 22 lists we hold that carry a date: 206 days (n=22); rank 1 = the most recently dated list. A month-only or two-digit version (for example “7.2026”) is shown as printed and not turned into a date.
Where the listed companies are based
247 companies on California lists print a town (247 of 552), spread over 119 towns. The most common:
- Sacramento: 25 companies
- Riverside: 13 companies
- Modesto: 10 companies
- Concord: 7 companies
- Roseville: 7 companies
- San Leandro: 7 companies
- East Bay Municipal Utility District: 6 of 82 companies with a printed town (7%) are in Oakland, the utility’s home city.
- Riverside Public Utilities: 13 of 89 companies with a printed town (15%) are in Riverside, the utility’s home city.
- City of Sacramento Dept of Utilities: 24 of 64 companies with a printed town (38%) are in Sacramento, the utility’s home city.
Computed from the 9 California utility lists above, as fetched 2026-11-04 (UTC). Towns as each list prints them; a company named on two lists counts once.
Companies on more than one list
16 companies of the 552 on California lists are named on more than one of them:
- Beaumont-Cherry Valley Water District and Irvine Ranch Water District: 1 company on both (2% of the first list, 1% of the second).
- Marin Water and East Bay Municipal Utility District: 4 companies on both (12% of the first list, 5% of the second).
- Marin Water and Riverside Public Utilities: 1 company on both (3% of the first list, 1% of the second).
- Marin Water and City of Sacramento Dept of Utilities: 1 company on both (3% of the first list, 2% of the second).
- City of Escondido Utilities, Water Division and Riverside Public Utilities: 6 companies on both (7% of the first list, 7% of the second).
- Irvine Ranch Water District and Riverside Public Utilities: 2 companies on both (2% of the first list, 2% of the second).
- East Bay Municipal Utility District and Diablo Water District: 2 companies on both (2% of the first list, 33% of the second).
- East Bay Municipal Utility District and Riverside Public Utilities: 1 company on both (1% of the first list, 1% of the second).
- East Bay Municipal Utility District and City of Sacramento Dept of Utilities: 2 companies on both (2% of the first list, 3% of the second).
- Riverside Public Utilities and City of Sacramento Dept of Utilities: 1 company on both (1% of the first list, 2% of the second).
Computed from the 9 California utility lists above, as fetched 2026-11-04 (UTC). Matched by our company record (same name plus a shared ZIP code or phone number on the lists).
What the lists print beyond names
- Beaumont-Cherry Valley Water District prints a tester certificate expiry date for 66 of 66 companies.
- East Bay Municipal Utility District prints a tester certificate expiry date for 82 of 82 companies.
We do not republish expiry dates; open the utility’s own list to check them.
Computed from the 9 California utility lists above, as fetched 2026-11-04 (UTC).
What kind of businesses are on the lists
The biggest difference from all the lists we hold: “backflow or cross-connection” appears in 58% of company names on California lists, against 24% across all of them.
| Company name contains | Companies (552) | Share | Share, all 2,590 companies we hold |
|---|---|---|---|
| Plumbing | 115 | 21% | 25% |
| Backflow or cross-connection | 318 | 58% | 24% |
| Fire | 28 | 5% | 17% |
| Irrigation, lawn, landscape or sprinkler | 23 | 4% | 10% |
| Mechanical, heating or air | 19 | 3% | 6% |
Computed from the 9 California utility lists above, as fetched 2026-11-04 (UTC). A company named on two lists counts once. A name can match more than one row; 87 names here match none. The words say nothing about the quality of the work.
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