Marine reverse osmosis watermaker fundamentals

Reverse osmosis (RO) watermakers push seawater through a semipermeable membrane at 800-1000 psi to produce fresh water. Core components: raw water pump (feed), high-pressure pump (usually a positive-displacement Cat or CAT pump), pressure vessels containing the membranes, and a product-water quality sensor. Typical output: 20-50 gph for a 12V system, 100-400 gph for AC-driven. Membrane life: 3-5 years in continuous use, longer with proper storage. Critical maintenance: (1) Prefilters (5-micron cartridge before high-pressure pump), replace when pressure drop exceeds 5 psi or monthly during regular use. (2) Membrane pickling or biocide storage when idle more than 5 days, bacterial growth destroys membranes. (3) Fresh water flush at end of every session, minimum 5-10 minutes with product water to purge salt. (4) Never run dry, the high-pressure pump seals rely on water lubrication. (5) Salinity probe calibration annually. Common failures: cracked pressure vessel end caps (over-pressurization), fouled prefilter causing pump cavitation, biofouled membrane after long storage without biocide.