Chances are a 5yr old sitting membrane is toast, so it's not all bad that you bought a new one. I wouldn't want to start my cruise
with a membrane that had been sitting for 5yrs...what was the maintenance history
before that..what is the real age of the membrane? On used water makers, this info is always hard to get from the preveious owner (at least honestly anyway...uggg)
The only real test to find out if a memberane is good or not is to run it. If the TDS level is below 500ppm (parts per million) as measured by a meter and the flow rate is within specs....bingo it is good. If you don't have a hand held TDS meter then BUY one! You can not go by the taste test because the level that salt
will hurt your kidneys is lower than the level it will start tasting "salty". You can buy them for cheap
...here is a link to one.
I've had membranes stored for just over 3 years and they worked fine...the problem is you typically have no way to know if the preveious owner really pickled the unit or...well....you know.
If RO Membranes dry out they are dead, gone, finished. The organic layer that does the actual "reverse osmosis" will crack and there is nothing you can do to clean or save the membrane. So part of the storage
on a membrane must keep it moist. The other factor of membrane storage
is keeping bacteria and microbes from growing out of control and destroying the membrane. "Pickling" is just a biocide or compound that kills the microbes/plankton/algae to keep biological growth from damaging the membrane, so nothing fancy there.
One CAUTION on pickling solutions.
Water makers use different pickling solutions based on their system components and although it is tempting to want to save money
and not use the pickling reagent recommend by the water maker manufacturer to save costs, if you don't know what you are doing the wrong pickling reagent CAN eat Hp pump seals and parts! So that savings in pickling reagent will cost you big time in a pump rebuild