Reverse Osmosis Membranes

MDC Water stocks reverse osmosis membranes for industrial and commercial systems across three grades — brackish water (BW), low-energy (LE), and seawater (SW) — in standard 1812, 4040 and 8040 element sizes. Australian stock since 1998 means replacement membranes ship on confirmed lead times rather than waiting on overseas supply.

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2.5″ x 21″ Reverse Osmosis Membrane Pressure Vessel – 300 PSI Used for 2521 RO...

2.5″ x 21″ Reverse Osmosis Membrane Pressure Vessel – 300 PSI

Used for 2521 RO membranes.

Ideal for residential, commercial, industrial, and marine-grade reverse osmosis systems.

Why Choose This Membrane Housing?

Reliable Pressure Performance: Built to withstand up to 300 PSI operating pressure in demanding environments.
Universal 2521 Fit: Designed for use with FilmTec TW30-2521, Vontron ULP21-2521 and other standard 2.5″ × 21″ RO membranes.
Built for Durability: Constructed from fiberglass-reinforced polymer (FRP) with protective polyurethane outer coating for long-lasting use and clean appearance.

What’s Included

Pressure Vessel Housing: FRP body with 2.5″ × 21″ dimensions
Mounting Hardware: Pads, straps, and brackets included for secure installation
End Caps: Two PVC end caps with 1/4" female feed/concentrate and permeate ports

Compatible With:

FilmTec TW30-2521 Membranes
Vontron, CSM, Hydranautics, Toray RO membranes
Other industry-standard 2521 membranes
Reverse osmosis systems in residential and commercial

Specifications

Size: 2.5″ diameter × 21″ length
Material: Fiberglass Reinforced Polymer (FRP)
End Port Connections: 1/4" female (PVC – feed/concentrate and permeate)
Outer Coating: White polyurethane for environmental resistance and clean aesthetics
Maximum Operating Pressure: 300 PSI
Shipping: Fast across Australia, fast delivery to New Zealand

Applications

Municipal and commercial water treatment
Oil & gas processing systems
Food & beverage production
Electronics and pharmaceutical industries
Power generation and mining sectors
Automotive and general commercial water systems

Get durable, high-pressure performance and universal compatibility with this 2521 membrane pressure vessel—ideal for land-based and marine RO applications.

$200.00

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Membrane Grades: Brackish, Low-Energy, Seawater

Reverse osmosis membranes split into three commercial grades — brackish, low-energy, and seawater — each matched to a feed-water TDS range and operating pressure. Brackish water (BW) membranes handle feed up to roughly 10,000 ppm TDS at typical operating pressures of 1,000 to 1,500 kPa. Low-energy (LE) membranes deliver similar rejection on brackish feed but at reduced operating pressure, lowering pump energy on softer feed water. Seawater (SW) membranes handle feed above 10,000 ppm TDS — including full seawater at 35,000+ ppm — and run at higher operating pressures, typically 5,500 to 7,000 kPa. Grade selection is the first decision; element size is the second.

Standard Element Sizes

RO membrane elements come in standard sizes — 1812, 4021, 4040 and 8040 — where the first two digits are diameter in inches and the last two are length in inches. The 1812 element is the residential and light-commercial standard for small RO systems. The 4021 and 4040 are mid-size commercial and small industrial elements. The 8040 is the industrial workhorse — used in commercial and industrial RO plants from food and beverage through municipal-scale desalination. Element size sets membrane area, which sets permeate flow at given operating pressure. Vessels are size-specific — an 8040 element does not fit a 4040 vessel.

Australian Stock & Replacement Compatibility

MDC Water holds Australian stock of brackish, low-energy and seawater RO membranes in 1812, 4040 and 8040 sizes for direct replacement. Stock depth means a membrane order placed during business hours typically ships the same day or next business day to metro Australia. RO membranes of matching size code are interchangeable across major OEM brands — replacement does not require sourcing from the original system manufacturer. Buyers replacing membranes on a third-party plant can match by size code and grade and order direct from MDC Water without OEM lock-in.

FAQs

Vontron ULP21-4021 Reverse Osmosis Membrane image 1

FAQs

01. What is a reverse osmosis membrane?

A reverse osmosis membrane is a semi-permeable thin-film composite that rejects 95–99% of dissolved salts under applied pressure. The membrane is wound into a spiral element with permeate channels and a feed-water flow path. Feed water entering at high pressure crosses the membrane as treated permeate; rejected salts and contaminants exit as concentrate. Element construction is similar across brackish, low-energy and seawater grades — the membrane chemistry differs by feed water class.

02. How long does a reverse osmosis membrane last?

Reverse osmosis membrane life typically runs three to seven years, set by feed-water quality, pre-treatment, and clean-in-place frequency. Membranes on well-pre-treated, low-fouling feed can run beyond five years. Membranes on high-foulant feed or insufficient pre-treatment may need replacement at two to three years. The right replacement trigger is salt passage rising above the system's design specification, not a fixed time interval.

03. What is the difference between BW, LE and SW RO membranes?

Brackish water (BW), low-energy (LE) and seawater (SW) RO membranes differ in feed-water TDS range and required operating pressure — BW and LE handle up to 10,000 ppm TDS, SW handles 35,000+ ppm. BW membranes are the default choice for most commercial and industrial sites running town or bore feed. LE membranes deliver the same rejection at lower pressure, cutting pump energy. SW membranes are reserved for desalination of brackish-to-seawater feed and run at much higher operating pressure.

04. How do I read RO membrane size codes like 4040 and 8040?

RO membrane size codes use four digits — the first two are element diameter in inches, the last two are element length in inches. A 4040 element is 4 inches in diameter and 40 inches long. An 8040 element is 8 inches in diameter and 40 inches long. A 1812 element is 1.8 inches in diameter and 12 inches long. Element diameter sets vessel diameter; element length sets active membrane area.

05. Are MDC Water RO membranes compatible with my existing system?

RO membranes of matching size code are interchangeable across major brands — a 4040 brackish membrane fits any vessel rated for a 4040 element regardless of OEM. The single hard compatibility constraint is the size code; brand and model are not constraints on physical fit. Match size code and grade against the existing system specification and the replacement will fit the vessel and deliver the rated flow.

Reverse Osmosis Membranes

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