No sailor wants to be caught in a situation where he or she is completely devoid of fresh drinking water. If onboard supplies run out or become contaminated, an emergency water desalinator can be the difference between survival and a slow death under the hot, unrelenting sun.
There are not a lot choices in the market for emergency watermakers. Obviously, the demand is focused in a very specific niche in the marine and emergency sector, meaning there is not an abundance of alternatives. One company, though, stands far above its competition.
The Katadyn Survivor 35 is the very best emergency watermaker.
This model uses a hand pump to force sea water at extremely high press through the reverse-osmosis membrane within the watermaker. The Survivor 35 can produce 1.2 Gallons of fresh water per hour, which is the highest output for manual-powered desalinators. According to the Katadyn website, with proper care, there is no expiration date for the membrane, which filters up to 98.4% of salt in sea water.
Reverse-osmosis is the same filtration process used to filter many brands of store-bought bottled water. The sea water is forced against the membrane at over 900 psi, forcing only the pure water through to the other side of the membrane. The membrane filters out salt, gunk and most other bacteria that contaminate sea water. The pure water that the Survivor 35 produces tastes surprisingly clean, and definitely no worse than Los Angeles tap water.
Katadyn originally made the Survivor line of desalinators because the U.S. Navy wanted hand-operated, reverse-osmosis watermaker for their 35-person life-rafts. The Survivor 35 is tough as nails, and differs only very slightly from the original Navy version. The unit has a solid heft to it, weighing in at seven pounds. For normal survival situations, the Survivor 35 is recommended for a 12-person life raft. It is also compact enough to fit into an emergency ditch bag.
Watercheck, a water conservation and safety blog, says, “[the] Katadyn Survivor 35 is the highest producing manual desalinator available in the world… Consider it low cost, affordable life insurance.”
The pumping action of the Survivor 35 did seem a bit rigorous during the first few tests, but the stress of repeated use with the long lever is placed mostly on the user’s larger back and arm muscles, which is more sustainable than using other methods of pumping. For example, the handheld version must be held in both hands while pumping, while the Survivor 35 can be placed on a hard surface, leaving one hand free during operation, although it can be a challenge to find a hard surface in a life raft. Also, the heavier pumping action produces four times as much pure water per hour than its handheld counterpart.
That brings us to the closest competition in emergency desalinators: The Katadyn Survivor 06. Its compact design is a great fit for personal life rafts. It can produce about one quart per hour if pumped constantly. The reverse-osmosis membrane is the same material in both the handheld version and the Survivor 35, but with extended use, the smaller membrane is more likely to break because of the extreme pressure.
In addition, the Survivor 06 has to be held between two hands, making it taxing on both arms, while the Survivor 35 can be placed on the deck, secured with a foot, and pumped with one hand. The Survivor 06 may be sufficient for solo survival, and it is definitely better than nothing, but for any more than one or two people it may prove to exceed its capabilities. The handheld version costs about half as much as the Survivor 35, but price is negligible if an entire crew of more than two needs enough water to survive.
The Survivor 06 is ideal size to be stored within a life raft in case of emergency, but it is recommended that it be kept in an abandon ship bag in case the life raft cannot be unpacked. It more practical to have the Survivor 35, though, because they both fit in an abandon ship bag, yet the Survivor 35 has twice the output.
Another much simpler alternative to the Survivor is the Solar Still. Aquamate makes a popular model that is semi-durable and comes in a bright orange color to help aid rescue. Sea water is held at the bottom of a floating clear plastic buoy. The heat from the sun makes the water evaporate, and condense into a receptacle, leaving the salt at the bottom of the buoy. It is certainly better than nothing, but at its maximum output, it barely produces enough water to keep one person hydrated, let alone an entire crew. It is also made of flimsy clear plastic, and the still is completely ruined with the slightest puncture, making it too fragile for extended use. Finally, it needs a stable environment to distill water, something nearly impossible to achieve in a bobbing life raft.
The final competitive product to the Survivors is the SeaPack Desalinator. It uses a process of forward-osmosis to bring pure water through a membrane. A sugar solution is placed on the outside of the membrane, and with heat and time, the pure water seeps through the membrane. Just the same as all of the other products, it is better than nothing, but the forward-osmosis process takes over 5 hours to produce just over a pint of water. The output water is distastefully sugary, and sustenance on such a liquid could lead to an upset stomach. The sugar solution that the SeaPack requires is also a serious limiting factor on its sustainability of pure water production.
Here is a chart from Landfall Navigation to compare the clean water production rates of the different models we tested:
As shown in the chart, the Survivor 35 produces nearly four times as much pure water per hour than its closest competition. Electric water makers are available that pump out far faster than the manual-powered models, but they are useless as soon as your power shuts down.
The Survivor 35 is one of the only products in its class, perhaps because Katadyn has done such a good job producing a rugged, lightweight desalinator capable of sustaining multiple people. When comparing other sea water desalinators, no consumer product comes close to the efficiency and quality of build.
Practical Sailor recommended Katadyn watermakers for all life rafts in their article “Six Man Life Raft Equipment Challenge”. The pure water produced from the Survivor 35 passes all EPA and Coast Guard standards for drinking water.