Shop around, ask different owners of present systems if they are happy with the machine's performance and take advantage of the mass of information on the Internet. If the seawater temperature is cooler than 77 degrees, production rate falls significantly. You will also experience a gradual loss of efficiency over the service life of the machine's membranes. Water makers will last longer if you install a unit that will satisfy your needs with a minimum of running time. Always be sure to operate the unit where there is no danger of picking up oil contaminated water.
Water making machines have other natural enemies, bacteria and biological growth in the membrane.
These machines perform best if operated briefly on a daily basis just to flush the membrane. If possible, the introduction of non-chlorinated water into the membrane to flush it will help slow the process. Change pre-filters as indicated by the feed water gauges. Higher numbered micron filters should be placed first in the path to the high-pressure pump. Plan on flushing the system with an acid and alkaline cleaner once a year to help remove residual biological growth and any mineral scaling that may build up in the system.