Bill & Bill, Thanks for explaining the numbers and their meaning. I really could not understand how the prefilters could be "special" , according to the dealer,thus the reason I asked my team of experts.

Another question: I have had two hoses made up by two different  hydraulic companies (the hose that runs from the membranes to the control panel) and neither have been able to supply stainless fittings. They have made them with steel fittings and rust quickly do to the salt water. Does anyone know somewhere I could have the hose made up with S.S. fittings and shipped to me?

Thanks,

Pat

SM Shenanigans

-----Original Message-----
From: Bill Kinney <cruisingconsulting@...>
To: main@AmelYachtOwners.groups.io
Sent: Mon, Sep 13, 2021 9:49 pm
Subject: Re: [AmelYachtOwners] Watermaker

Pat,

I can assure you that there is nothing at all "special" about the prefilters used for a watermater. A 5 micron rated filter will do fine. If you have dual filter housings in series, a 20 or 25 micron in the first chamber will catch the "big" stuff.  You'll generally do better with the pleated paper elements than the filament wound ones, but it's not critical.

I am betting that the guy who told you you needed "special" watermaker prefilters just happened to have some of these magic filters he was happy to sell you. I'd take all the advice you got from him with a very large dose of salt.

Although they are not expensive, in an emergency you can reuse them at least once or twice.  Put a line down the filter, tie a stopper knot , and tow them behind the boat.  The resulting "backwards" flow through the element does a good job at cleaning them if they are not too far gone.

Bill Kinney
SM160, Harmonie
Annapolis, MD, USA