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Ozmosis Brand 4″ x 21″ Brackish Water – Universal High-Pressure Membrane
Optimal Pressure 225 PSI (90-300PSI)
Its Average GPD is 1,000
Salt Rejection Rate 99.6%
Made of the highest quality materials including Toray Brand Sheets

Coastal Water Filters is proud to offer the Ozmosis brand seawater membrane, brand new in a factory sealed box. It outperforms Dow TW30-4021 and Dow TW30-4021. CSM RE4021-BLN. This membrane is designed to produce high quality water at extremely low pressure. The test results are given at 150 psi, but the water is produced at a much lower pressure. 1000 g/day at 225 psi and 1000 g/day 99.6% salt rejection means that this will give more water, better quality water, and use less energy (electricity) to produce that water.

Versatile Applications: BW-4021 reverse osmosis membrane is suitable for a variety of applications including car wash, irrigation, food industry, domestic and commercial reverse osmosis, and agriculture and industry.

Universal Fit: Designed to measure 4″ x 21″, easily fits into any standard 4″ x 21″ fiberglass diaphragm housing for a perfect fit.

Suitable Brand Compatibility: Compatible with Suitable brands such as Dow Filmtec, CSM, Toray, Hydranautics and Axeon Seawater Series, this membrane offers superior performance.

High-quality materials: Made from the finest materials, including Toray brand panels and Dow brand adhesives, this membrane combines the best features of both manufacturers to ensure long-lasting quality.

Exceptional performance: with an average production speed of 1000 GPD , a remarkable 99.With a salt retention rate of 2% and a recovery rate of 15%, this membrane is ideal for even the most demanding tasks. The fiberglass housing offers superior durability compared to plastic housings, ensuring reliability and solid filtration.

The Ozmosis RO Reverse Osmosis Membrane BW-4021 stands as a dependable and efficient water treatment solution. Its compact 4″ x 21″ design offers versatility, making it ideal for various applications. With a focus on water purity and quality, this membrane ensures that your water treatment needs are met with excellence. By choosing the BW-4021, you’re investing in a reliable and innovative solution that guarantees the supply of clean, clear water.

Additional information



Salt Rejection


Average Production

1000 GPD

Max Pressure

600 psi

Optimal Pressure

225 psi


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