Home / Backflow testers / California

Oakley backflow testing

6 companies on Diablo Water District's tester list · company-level list (no tester count) · list version Effective September 21, 2026

About this list

Utility
Diablo Water District
List title
“List of Certified Backflow Testers” (as printed)
Version
Effective September 21, 2026
List date
2026-09-21
Fetched
2026-11-04 (UTC)
Format
PDF
Testers
Company-level list (no tester count). Every entry on this list is a company.
Gaps
Our copy of Diablo Water District's list (version Effective September 21, 2026), fetched 2026-11-04, no phone for 1 of the 6 companies (the list prints none for them, or prints a number labelled as a mobile on a list we read, which we do not republish). Those cards leave the field out.

On Diablo Water District's approved list, version Effective September 21, 2026 · fetched 2026-11-04

Every company below is on this list; each card says “On this utility's approved list”. The list is the utility’s, not ours: we copy company names, addresses and phone numbers from it, sort them A to Z and do not rank or endorse anyone. Confirm with your utility before booking.

On the list as ofEffective September 21, 2026

List of Certified Backflow Testers. Fetched 2026-11-04 (UTC).

Open the utility’s own list
The utility’s backflow program page
How we handle listings (correct or remove a listing)

Confirm with your utility before booking.

Companies on the list (6)

Alphabetical. Company-level list (no tester count): the utility lists companies, not individual testers.

Thorpe Design Inc

410 Beatrice Court, Ste A, Brentwood, CA 94513925-848-6432

On this utility's approved list

From its website (2026-11-15): also fire sprinklers, other fire protection; serves homes; area: Proudly Serving California and Nevada.

Other utility lists in California: Beaumont, Corte Madera, Escondido, Irvine, Modesto, Oakland, Riverside, Sacramento.

Guides: How much does a backflow test cost? Tester prices, plus what your utility adds, Failed backflow test: what failed, your repair deadline, and when to replace the device, What is a backflow test? What the tester measures, what passes, and what you have to do, Irrigation backflow testing: which device your sprinkler system needs, when it is tested, and how to winterize it.