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Handheld desalinators operating on the principle of reverse osmosis are available for emergency use in lifeboats. Sometimes they appear for sale unused in their original packaging at a very steep discount because they have been replaced at a scheduled interval by their owners (merchant marines, navies, etc). Is there any reliable means to assess the condition of the device and determine if it is reliable enough either for convenience (reducing the quantity of fresh water carried) or for possible life-sustaining use? Checking the condition of mechanical parts (pivots, levers, body) and of any seals (no cracks) seems straightforward, but what about the reverse osmosis membrane itself?

(Inspired by Portable desalination hand pump filter life?)

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You can test it at home.

Make you own salt water by adding 35grams of salt to a liter of water.

Desalinate the water to a new container, and measure the salinity with a hydrometer. one of lots of google hits, as example

You should also be able to taste the difference. Be aware there could still be a flaw in the osmosic barrier that allows an occasional; bacteria, virus, etc through as well as trace amounts of salt. Even if you can't taste or measure the salt with a hydrometer there may still be some. You may or may not want to use a secondary purification process that would not normally be required with reverse osmosis

Related How much sea water can I safely drink?

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  • After use a certain amount of maintenance is required.
    – paparazzo
    Oct 2, 2018 at 14:32
  • @James Jenkins Yeah my concern is that the failure mode might be like an aging bicycle tire—after years in the garage it seems to take air just fine but is in fact brittle and prone to a sudden sidewall blowout compared to a new tire—with a bike tire I just flex in my hands and look for cracking, wondering what is the RO-membrane equivalent.
    – mmcc
    Oct 2, 2018 at 17:56
  • @mmcc Bike tires and RO membranes are not good one day and bad the next. On some date, the likelihood of catastrophic failure increases to a point that risks outway the benefits. Alternately like some software, hardware can have pre planned expiration date purely for business reasons, they need to sell a new one every #years to stay in business.
    – James Jenkins
    Oct 2, 2018 at 18:12
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Many recommend send for inspection yearly. katadyn

Factor that into the price and decide if it is still a good deal.

IMPORTANT: For your safety, we require that an inspection be completed once a year. Our regional service centers are trained to perform all necessary quality checks or you can return the unit to Katadyn for inspection.

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  • yeah my question is basically what are they inspecting and is it realistic to learn to perform that inspection yourself.
    – mmcc
    Oct 2, 2018 at 16:17
  • @mmcc You really want to do your own safety check on something that critical?
    – paparazzo
    Oct 2, 2018 at 16:24
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    Maybe. I have less knowledge than the factory technician but more incentive to do the work correctly and ability to do it frequently. So like car repair it depends on how much training is required to do it right. Which is what I do not know. Maybe someone reading this will know.
    – mmcc
    Oct 2, 2018 at 17:45

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