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RO Membrane Selection for Los Fresnos, TX Water

City of Los Fresnos
PWS ID: TX0310004
2025 water quality report

What's in Los Fresnos's Water

Reported values from City of Los Fresnos's 2025 water quality data. Feed water chemistry drives membrane choice, operating pressure, and cleaning frequency.

Source water

Rio Grande surface water treated at the city reservoir, blended with purchased groundwater from the Southmost Regional Water Authority RO desalination plant in Brownsville; emergency interconnect with East Rio Hondo WSC

Arsenic4 ppb
Barium0.0021 ppm
Chlorine2.31 ppm
Copper 90th0.0277 ppm
Cyanide100 ppb
Dibromochloromethane37.1 µg/L
Fluoride0.2 ppm
HAA523 ppb
HAA5 (range)20.4-24.9 ppb
Lead 90th1.76 ppb
Selenium10 ppb
TTHM37 ppb
TTHM (range)35-46.8 across two sites ppb

Our Recommendation for Los Fresnos

Los Fresnos' standout number is cyanide at 100 ppb — fully compliant but sitting at half the 200 ppb federal limit, the highest in the Valley batch — alongside selenium at 10 ppb and arsenic at 4. RO rejects all three; the brackish NanoH2O (formerly LG) BW 400 R G2 is the fit for this Rio Grande feed. Notably, part of the city's supply already comes from the SRWA's RO desalination plant — the technology is literally already in the water.

Membranes Matched to This Water

The Industry Workhorse

NanoH2O (LG) BW 400 R G2

  • 99.8% salt rejection
  • 11,500 GPD · 225 psi
  • 400 ft² active area
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Running RO on Los Fresnos water?

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Data Source

Water quality values on this page are taken from City of Los Fresnos's 2025 published water quality report (PWS ID TX0310004). Values are utility-wide averages; water at a specific site can vary. For membrane selection on a critical system, test your actual feed water.

View the official report