8" Membranes

8" Reverse Osmosis Membranes

8" reverse osmosis (RO) membranes are the industry standard for commercial and industrial RO systems requiring high daily water production and consistent performance. Commonly available in sizes such as 8040, these membranes are designed to operate at higher flow rates while maintaining excellent salt rejection and long service life under demanding conditions.

8" RO membranes are widely used in applications including:

  • Industrial water treatment systems
  • Commercial RO installations
  • Manufacturing and process water
  • Food & beverage production
  • Brackish water desalination
  • Pretreatment for specialty water applications

At Knapp RO Chicago, we stock genuine 8" RO membrane elements from leading manufacturers including DuPont / FilmTec, Hydranautics, LG, and others. Each product listing includes manufacturer-rated specifications such as flow capacity (GPD), salt rejection, operating pressure, and application type to help ensure proper system compatibility.

Because 8" membranes represent a significant investment, selecting the correct element is critical. Factors such as feed water TDS, system pressure, recovery rate, and pretreatment quality all play a major role in membrane performance and lifespan.

Browse our current selection below, or review the guidance at the bottom of this page to help choose the right 8" RO membrane for your system.
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How to Choose the Right 8" RO Membrane

Selecting the correct 8" reverse osmosis membrane requires careful evaluation of system design and feed water conditions. Using the wrong membrane can reduce throughput, increase operating costs, or shorten membrane life.

Common 8" RO Membrane Sizes

  • 8040 – Industry standard for commercial and industrial RO systems
  • Always confirm housing length and element configuration before purchasing

Flow Rate & Production Capacity

8" membranes are designed for high daily production, often exceeding several thousand gallons per day. Higher flow membranes may require increased feed pressure and optimized system design.

Salt Rejection & Water Quality

Standard 8" membranes typically offer 99% salt rejection, while specialty membranes may be optimized for:

  • High rejection
  • Low energy operation
  • Brackish water feed
  • High fouling resistance

Selecting the correct rejection profile depends on feed water TDS and end-use requirements.

Operating Pressure & Pretreatment

Feed pressure, temperature, silt density index (SDI), and chlorine exposure all directly impact membrane performance. Proper pretreatment — including multimedia filtration, carbon filtration, and softening where required — is essential to protect 8" membranes and maximize service life.

Brand & System Compatibility

Most 8" membranes are interchangeable across standard pressure vessels, but performance characteristics vary by manufacturer. Matching replacement membranes to the original brand and model is often the safest approach for system stability and performance consistency.

Frequently Asked Questions

How long does an 8" RO membrane last?

With proper pretreatment and operating conditions, most 8" membranes last 3–5 years.

Can I upgrade to a higher-capacity membrane?

Possibly — but only if your system can support the required pressure, recovery rate, and hydraulic conditions.

Are 8" membranes suitable for brackish water?

Yes. Many 8" membranes are specifically designed for brackish water applications. Always verify manufacturer specifications.

Do you sell genuine manufacturer membranes?

Yes. All 8" membranes sold by Knapp RO Chicago are authentic manufacturer products, not relabeled or generic elements.