Re: Dessalator Watermakers & Filmtec Membranes

Patrick McAneny

Craig, I should not have used psi to convey what I meant, I always operate my W/M  at the low end of the green zone in salt water, and in fresh water the couple of times I have ran it just to be sure it was functional ,I kept the pressure slightly below the green zone. I don't even know what the psi is at the green zone . I just made sure that it did not go into the green or exceed normal water production level. Once again I only ran it for a short period to confirm functionality .
It obviously takes less psi to push fresh water thru the membranes and that is what I was trying to convey and was warned about by the manufacturer. Having said that ,he said providing you don't exceed the pressure limits ,it was fine to use your W/M in fresh water ,and many do.

-----Original Message-----
From: Craig Briggs via <sangaris@...>
Sent: Thu, Sep 10, 2020 1:13 am
Subject: Re: [AmelYachtOwners] Dessalator Watermakers & Filmtec Membranes

Hi Pat,
If you run 800 psi in fresh water you will definitely damage your membrane. You want to limit the product water flow to that rated for the membrane in terms of LPH or GPH, definitely not the 800 +/- PSI for ocean water.  
Your sentence about "keep it a little lower and warning that it will get up to "max" more quickly" is telling - "max" is the maximum flow for the membrane, and that is reached at very low pressure in fresh water. The words "keep it a little lower" are hugely understated, as 200-300 psi is typically the fresh water range.  Actually, household RO systems operate without any pump at all, just the water service pressure in the range of 35 psi or so. 
SN68 Sangaris, Tropic Isle Harbor, FL

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