Brackish water membranes, explained

A brackish water membrane, often shortened to BW or BWRO, is a reverse osmosis element built for feed water that carries more dissolved salt than town mains but far less than the sea: saline bores, groundwater, and the estuarine and process feeds in between. It is the middle grade of the three. Low energy elements suit low-salinity feed, seawater elements handle desalination duty, and brackish elements cover the saline ground between them, running at higher feed pressure than low energy to reject the extra salt. In Australia that makes brackish the workhorse grade for groundwater: bore water desalination for livestock, dairies and horticulture, potable plants at remote mine and exploration camps, containerised community treatment plants, and process RO in food and drink production. If you are replacing, match the grade and code of the element you are taking out. If you are not sure your water is brackish duty, send us your feed water details and we will recommend an element, including telling you when brackish is not the grade your water needs.

The range: FilmTec, Hydranautics, LG and Trilite

Every brackish element we stock is listed here by model code, and each product page carries the full specification for that model, including its flow, rejection and operating pressure figures.

• FilmTec (DuPont): BW30 PRO-4040, BW30-4040, BW30-400
• Hydranautics: CPA5-LD-4040, CPA5-LD
• LG Chem: BW 4040 R
• Trilite: BWHR-4040

If the code you are replacing is not here, send it to us and we will quote the closest match with a spec comparison, so you can see exactly what differs before you decide. That includes the honest answer when a substitution is not a good fit for your duty.

Sizes: 4040 and 8040

The size code on an element describes its nominal diameter and length, and the dimensions are industry standard, so a 4040 from any major maker installs into the same nominal 4 inch pressure vessel. In this range the 4040 is the 4 inch format and the depth of the range, with every stocked brand represented, and the 8040 is the 8 inch format for larger plant, covered by the FilmTec BW30-400 and the Hydranautics CPA5-LD. Use the size and flow rate filters above to narrow the grid, and match the code printed on the element you are taking out before you order. The small membranes inside household undersink RO systems are a compact format that is not part of this industrial range.

Cleaning and when to replace

Industry references put typical membrane life at 2 to 5 years for well-run industrial RO on brackish feed, depending on feed quality, pretreatment and cleaning practice. Treat that as a planning figure and let performance decide. Membrane manufacturers' cleaning guidance is to clean when normalised permeate flow falls around 10 percent from baseline, and to replace when cleaning no longer restores performance. Bore feeds deserve extra attention here: hard, iron-bearing bore water scales and fouls membranes faster than town water, so pretreatment earns its keep before the element does. If a brand-new element still gives poor water, check pretreatment, pressure and recovery before replacing again, or ask us to look at the numbers with you.

Supply for Australian industry

MDC Water has supplied membranes and water treatment components to defence and government facilities, universities, food and drink production, and energy utilities across Australia and overseas since 1998. In-stock items dispatch next business day, and pricing is on every product page so you can compare before you order. We handle formal quotes, tax invoices, vendor onboarding paperwork and freight quotes to remote sites. Housings are in the membrane pressure vessels range if you are replacing those too, lower-salinity duties are covered in low energy RO membranes, seawater duty is in seawater RO membranes, and the full membrane range across all three grades is at reverse osmosis membranes.