This isn't about how to make a desalinator, just how to prepare it for storage so it so it'll work a year later.
A reverse-osmosis desalinator makes seawater safe to drink by removing almost all of the salt.
It does this by forcing the water through a semipermeable membrane at high pressure.
The water passes through the micropores of the membrane but the salt does not.
I bought a "Survivor 06" hand-pumped unit for a very good price at http://www.nauticaltrader.net/ , a marine consignment store in Venice, Florida.
After almost a year I mixed some table salt with tapwater and tried it out. Much to my surprise it worked perfectly. Unfortunately within a few days there were visible clumps of living stuff growing in the output hose. The water it produced had a bit of a "garden hose" taste to it.
So I consulted the manual ( of all things ) to see what to do.
The manual says to pump some water containing the right kind of biocide into it before storage.
Scroll down to see the link to the pdf manual for this unit
Step 1: What the Manual Says
From the manual:
Storage (7 days or longer)
The Survivor06 is shipped from the factory with a biocide solution inside, to prevent the growth
of bacteria. After the unit has been operated and before it is stored again, it should be flushed with
biocide as outlined below.
IMPORTANT: Never let the membrane dry out. Be sure to follow these storage instructions.
1. Turn the unit upside down, with the intake strainer out of the water.
2. Fill a suitable container with about a quart (approximate 1 liter) of clean water. Freshwater is
preferable, but clean seawater can be used if freshwater is not available.
3. Mix one spoonful (10 grams) of the biocide with water until dissolved.
4. Place the intake strainer into the biocide solution, and pump until water starts flowing out of the
reject hose (indicating that the membrane housing is filled). Stop pumping immediately after
water begins to flow from the reject hose.
5. If seawater was used to mix the biocide solution, repeat the above procedure with freshwater
as soon as it is available.
6. Rinse any biocide solution off the outside of the unit. Allow the unit to dry completely before
IMPORTANT: For your safety, we require that the above procedure be completed once a year
(storage temperature < 25°C/77°F). Please be aware to use only biocides supplied by Katadyn
for your product. Other products like chlorinebased products will damage your membrane.
The bottle of biocide says: Active ingredients: Sodium Chloride, Citric Acid Anhydrous and Sodium DBSA
Here are some shots of the other text printed on the bottle. The label wraps around the side so it's a bit of a hassle to read in these shots, but oh well.
Step 2: So That's What I Did
I did just that, following the directions.
Afterwards I didn't know what to do with the left over biocide mixture so I poured it back into a water bottle labeled "biocide for desalinator"
Desalinator is now ready for one year of storage.
When next I sail on some half-planned odyssey I'll bring this along and maybe it'll save my life. At least the boat will be lighter because I won't be bringing so much water along. I'll only bring as much as I need instead of as much as I MIGHT need like I do now.
The manual says this unit can produce up to 6 gallons per day.
That would be a lot of pumping, but not as much work as you'd think. There's a pressure-relief valve protecting the membrane so pumping harder doesn't get you any more results, just more tired.
There's 800psi somewhere inside this little pump, but you wouldn't know it.
It doesn't feel like pumping a bike pump or a hydraulic jack. It feels more like a water pump.
Pumping with both hands is probably great for your pects but is twice the work of resting it on something and pumping with one hand. If you tied it down to a bench you'd probably pump a day's water just by fidgeting.
Timo Noko ( hero and role model ) set one up with a Cretan Windmill to pump by windpower.
http://koti.welho.com/tnoko/ -scroll down to "pur 06".