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Wayne.B

On Mon, 24 Aug 2015 23:54:35 -0400, wrote:

I was never sure why it should cost that much. I guess running RO from
sea water is tougher than brackish well water.
Basically you just need a high pressure pump and a membrane/vessel for
that along with intake and polishing filters.
Since you are not really pumping that much water, I suppose it could
run off the house battery.

===

It takes more pressure as salinity levels go up, much more, something
like 2,000 psi for standard sea water. It takes special membranes to
stand up to that kind of pressure and a lot of power to drive the
pump, typically several horsepower. The pumps will not run very long
from a battery.

The membranes are expensive and require special maintenance routines
to maintain their effectiveness. That involves a lot of extra valves
and plumbing. The better units also have computerized controls to
automate the maintenance routines.

Some guys have tried to homebrew inexpensive systems using pressure
washer pumps but the pumps fail very quickly in a salt water
environment.