How often should I replace the water filters on Grace's Enwa watermaker?

Replace Grace's Enwa seawater prefilters when they become fouled or restrict the feed supply, rather than after a fixed number of weeks. Check their condition and feed pressure at every run, and identify the exact Enwa model before setting separate replacement intervals for carbon filters or other cartridges.

Identify Grace's filters

Check the model plate, cartridge labels and pipework. The seawater strainer, sediment prefilters, freshwater-flush carbon filter and reverse-osmosis membranes do different jobs. A replacement schedule for one does not apply to the others.

• Seawater strainer: usually a reusable mesh basket or screen; clean it when debris accumulates.
• Sediment prefilters: replaceable cartridges that protect the pumps and membranes from suspended particles.
• Flush-water carbon filter: if fitted, removes chlorine from freshwater used to flush the membranes.
• Reverse-osmosis membranes: assess these by performance and water quality; they are not routine sediment-filter consumables.

The supplied information does not identify Grace's Enwa model or its specified service intervals. Do not use another manufacturer's cartridge sizes, pressure limits or flushing schedule. Photograph the model plate and existing cartridge markings before ordering spares.

Time prefilter changes by condition

With clean cartridges fitted, record the normal feed pressure, seawater temperature and freshwater output once the machine has settled into operation. Use those readings as a baseline to spot deterioration.

If there are gauges before and after the prefilters, watch the pressure difference between them. A growing difference indicates restriction. With only a downstream feed gauge, falling pressure can indicate blocked filters, but it can also point to a blocked strainer, restricted intake, air leak or feed-pump fault. Use the service threshold in the Enwa manual. There is no reliable universal pressure figure.

• Before each run: check the strainer and visible cartridge condition, and look for leaks.
• During each run: check feed pressure or the filter-condition indication, alongside product flow.
• Replace promptly: when the specified restriction limit is reached, cartridges become heavily fouled, or slime and persistent odour develop.

Clean offshore water can give weeks of service or longer. Heavy suspended sediment can foul a cartridge within hours. These are possible service lives, not Enwa replacement intervals. Reduced freshwater output alone does not prove a blocked filter: colder seawater also reduces production.

Separate cartridge and membrane maintenance

Match each replacement cartridge's length, diameter, micron rating and construction to the installed specification. Some watermakers use coarse and fine filtration in stages. Check before assuming Grace needs a particular combination: a finer cartridge can increase restriction.