Hydranautics, a Nitto Group company, makes the SWC family of seawater reverse osmosis elements. Meliora sources SWC4, SWC5 and SWC6 elements in LD and MAX versions for replacement and for new trains, from single-vessel quantities to full membrane changes.
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In short: The Hydranautics SWC family has three membrane types, SWC4, SWC5 and SWC6, each offered as an LD element with 400 ft² of active area and a MAX element with 440 ft². Meliora sources all of them. To replace existing elements, send the model printed on the element label and the quantity.
The figures below are the nominal values Hydranautics publishes for its 8-inch seawater elements.
| Element | Active area | Permeate flow | Nominal salt rejection | Feed spacer |
|---|---|---|---|---|
| SWC4-LD | 400 ft² (37.2 m²) | 6,500 gpd (24.6 m³/d) | 99.8% | 34 mil |
| SWC4 MAX | 440 ft² (40.9 m²) | 7,200 gpd (27.3 m³/d) | 99.8% | 26–28 mil |
| SWC5-LD | 400 ft² (37.2 m²) | 9,000 gpd (34.1 m³/d) | 99.8% | 34 mil |
| SWC5 MAX | 440 ft² (40.9 m²) | 9,900 gpd (37.5 m³/d) | 99.8% | 26–28 mil |
| SWC6-LD | 400 ft² (37.2 m²) | 6,000–12,000 gpd (22.7–45.5 m³/d) | 99.6% | 34 mil |
| SWC6 MAX | 440 ft² (40.9 m²) | 6,600–13,200 gpd (25–50 m³/d) | 99.6% | 26–28 mil |
Source: Hydranautics SWC family brochure. Hydranautics also lists a 4-inch SWC5-LD-4040 (80 ft², 1,750 gpd, 99.7%) and 16-inch SWC4 and SWC5 elements.
SWC4, SWC5, SWC6. These are three membrane types with different trade-offs between water production and salt rejection. In the published figures, SWC4 produces the least water per element, SWC5 produces more at the same nominal rejection, and SWC6 has the highest flow range at a slightly lower rejection of 99.6%.
LD. LD stands for low differential. These elements use a thicker 34 mil feed spacer. Hydranautics offers them to reduce colloidal fouling on plants with conventional pre-treatment, and states that they give low feed pressures and the longest time between cleanings.
MAX. MAX elements fit 440 ft² of membrane into the same 8-inch element, which is 10% more area than the LD version, using a thinner 26 to 28 mil spacer. Hydranautics describes them as giving high salt and boron removal from warm waters, which is the condition Gulf plants operate in.
The safe replacement is the same model that is installed. The model and serial number are printed on the label on each element. If the label is unreadable, the plant’s commissioning documents or membrane projection will state the model.
Changing model is a design decision and not a purchasing one. An LD element and a MAX element are the same size and will physically fit the same pressure vessel, but they have different area and different spacers, so the train will run at a different pressure and recovery. Mixing them in one vessel changes how the flow distributes between elements. If the plant wants to change model, or if the installed model is no longer made, we put the question to the manufacturer with your feed water data and let them propose the element.
The same applies when replacing another manufacturer’s element with a Hydranautics one. We supply DuPont FilmTec and Toray elements as well, so there is no need to change brand just to get supply.
Tell us which of these you are doing. It changes how the elements should be shipped, and for a full train the manufacturer may need to schedule production.
Replacing Hydranautics elements? Send the model and quantity. Plant-down enquiries get a reply within 4 hours, standard quotations within 48 hours.
Page reviewed October 2026 · Meliora FZCO, Dubai Silicon Oasis, UAE
They are three seawater membrane types with different flow and rejection. In the 400 square foot LD version, SWC4-LD is rated 6,500 gallons per day at 99.8% nominal rejection, SWC5-LD 9,000 gallons per day at 99.8%, and SWC6-LD 6,000 to 12,000 gallons per day at 99.6%.
LD means low differential. LD elements use a thicker 34 mil feed spacer to reduce colloidal fouling on plants with conventional pre-treatment. Hydranautics states they offer low feed pressures and the longest duration between cleanings.
MAX elements have 440 square feet (40.9 square metres) of active membrane area in a standard 8-inch element, compared with 400 square feet in the LD version. Hydranautics describes them as providing high TDS and boron removal from warm waters.
They are the same physical size, but the MAX element has 10% more membrane area and a thinner feed spacer, so the system will operate differently. Treat it as a design change and have the manufacturer confirm it against your feed water data before ordering.
Yes. We quote from single elements for a damaged vessel up to complete trains for a planned membrane change.