Water measurement firm plans November shutdown affecting all 36 local employees
September 4th, 2026: SonTek files WARN noticeNew here? Follow stories to track developments over time. Create a free account to get updates when stories you care about change.
Overview
Updated 1 hour agoSonTek, the San Diego maker of acoustic Doppler instruments that measure river flow and ocean currents, filed a California WARN notice Thursday to close its local site. The shutdown is dated November 6 and affects all 36 employees on staff.
SonTek came under Xylem through the water giant's 2012 purchase of YSI, which had owned SonTek since 2004. The closure fits a pattern: Xylem has been folding the instrument brands it accumulated through acquisition into fewer facilities.
Why it matters
The closure ends a 36-year San Diego maker of river and ocean current meters, signaling Xylem's consolidation of the brands it bought into fewer sites.
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People Involved
Organizations Involved
Makes acoustic Doppler current profilers and flow meters used to measure water velocity in rivers, oceans, and wastewater systems.
Global water infrastructure and instrumentation company, formed from ITT's water businesses.
California's labor agency, which administers the state's Worker Adjustment and Retraining Notification (WARN) program for mass layoffs and plant closures.
Timeline
January 1990 November 2026
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Planned closure date
Upcoming MilestoneThe San Diego facility shutdown is scheduled to take effect, ending SonTek's local run.
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SonTek files WARN notice
Latest Regulatory FilingSonTek notifies California of its plan to close the San Diego site, affecting 36 employees.
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Xylem acquires YSI
AcquisitionXylem completes its purchase of YSI, bringing SonTek under the Xylem umbrella.
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YSI acquires SonTek
AcquisitionYSI Inc. buys SonTek, folding the San Diego firm into its water monitoring portfolio.
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SonTek founded in San Diego
FoundingEngineers who left RD Instruments start an acoustic Doppler current profiler maker.
Scenarios
Xylem relocates SonTek production, keeps brand alive
Discussed by: Water industry analysts and former SonTek staff
Xylem moves the remaining SonTek current profiler and flow product lines to another facility, likely its YSI site in Ohio or a Texas plant. The SonTek brand stays on the market, but the San Diego jobs end as scheduled on November 6.
SonTek brand phases out, products fold into Xylem Analytics
Discussed by: Instrument industry analysts
Xylem retires the SonTek name entirely. The acoustic Doppler product lines fold under Xylem's analytics portfolio, and the San Diego closure is the final step of that integration. Customers buy the same hardware under different branding.
Closure delayed or rescinded
Discussed by: Workforce and labor analysts
Part or all of the November shutdown is postponed, due to order backlogs, efforts to retain key engineers, or local pressure. A revised notice or withdrawal appears on the EDD WARN list before the closure date.
Historical Context
3 moments from history that rhyme with this story — and how they unfolded.
RD Instruments joins Teledyne (2004)
RD Instruments (RDI), SonTek's hometown rival in San Diego acoustic Doppler current profiling, was acquired by Teledyne Technologies. The two firms had competed for decades on ocean and river measurement hardware.
RDI became part of Teledyne Marine, keeping its brand and San Diego-area base.
The acoustic Doppler profiler market settled into two conglomerate-owned camps: Teledyne with RDI, and Xylem with SonTek.
Shows how independent instrument makers that once competed in San Diego got absorbed by larger firms, setting the stage for consolidation decisions like the SonTek closure.
ITT spins off Xylem (2011)
ITT Corporation split into three companies, with its water businesses becoming Xylem Inc., a pure-play water technology firm listed on the New York Stock Exchange.
Xylem began life with a portfolio of inherited water brands and no legacy of its own manufacturing footprint.
The structure gave Xylem a mandate to grow by acquisition and later rationalize brands, which is how it bought YSI and eventually closed the SonTek site.
Explains why SonTek is owned by a consolidation-focused water conglomerate rather than operating as an independent San Diego firm.
Xylem buys YSI, inherits SonTek (2012)
Xylem acquired YSI Inc., the Ohio-based water quality monitoring company that had owned SonTek since 2004. The deal brought SonTek's acoustic Doppler product line into Xylem's analytics group.
SonTek became a smaller brand inside a much larger portfolio, with its San Diego site one of many Xylem facilities.
The acquisition created the integration pressure that later surfaced as facility closures when Xylem sought cost savings.
This is the mechanism that put SonTek under Xylem; the 2026 closure is the late-stage consequence of that 2012 integration.
