When backpacking in a coastal region, you sometimes have access to both fresh water (e.g. a stream) and salt water (sea, bay, etc.).

If you do not treat the water used for washing dishes, what are the pros and cons of using saltwater vs. freshwater? Is there one source that is less prone to contamination?

The choice is easy if the shoreline is polluted or the stream is next to a privy (established or... improvised). However, when there are no obvious differences in water quality, which one would be more recommended and why?

  • "If you do not treat the water used for washing dishes" -- Incredibly bad idea. What is the point of purifying water to drink if you are going to contaminate everything else? Commented May 13, 2013 at 15:40
  • A worded the question so that it doesn't imply whether you treat the water you drink. I believe what you pointed out would be a good question on its own.
    – ppl
    Commented May 13, 2013 at 16:35
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    @ppl, ncbi.nlm.nih.gov/pmc/articles/PMC145303 has some info on what viruses can live in seawater and some estimates of how dangerous levels are, and it's quite clear that you can get stomach bugs from sea water. It doesn't really answer your question, though. I'd also want to know how long can dangerous things survive on a dry surface.
    – Karen
    Commented Oct 20, 2017 at 13:15

3 Answers 3


Leaving aside the questions of water purity, then the answer would be fresh water, no question.

Salt water does not lather up many soaps very well, although detergents are a different story. Salt water also does not rinse cleanly, so even those long-distance sailors that use salt and Joy detergent (no corporate affiliation, but lots of online reading) use (clean) fresh to rinse.

So, fresh it is. (But purify somehow, by boiling if by nothing else)

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    Great information about the sudsing and rinsing. Good to know! Commented May 15, 2013 at 13:38

Seawater typically has more organisms growing in it than a flowing stream of clear water. However, it's a good idea to use something (boiling, wet ones, clorox wipes, etc.) that kills giardia, microspiridia, and other protozoa or bacteria than can give you the diarrhea.

  • Does seawater generally has more harmful organisms than stream water? For example, is it not less likely to have giardia in seawater compared to lake or stream water?
    – ppl
    Commented May 14, 2013 at 17:16
  • Coastal seawater sometimes has harmful organisms from sewage and animal waste -- enough for beach closures. I don't know any statistics or specifics. Just because it's salty does not mean bad stuff won't grow in it.
    – xpda
    Commented May 15, 2013 at 5:19
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    The question states all things being equal. Today I had the opportunity to ask biology professor the question. Of the top of his head, he would favor the sea water because of a (presumably) lower likelihood of encountering human pathogens. I understand that the salinity of the water does not prevent growth of all (or any) pathogens. However I would hypothesize that it have an influence on some relevant pathogens listed in the answer. I would be interested if somebody could shed some light on this aspect of the question with possibly data or scientific references.
    – ppl
    Commented May 16, 2013 at 2:41

You should never plan to not purify. Levels of contamination will depend on the location. A stream running by a pasture 50 miles upstream will possibly contain more contaminants than ocean, even if the ocean (on average) is worse.

If you have a way to purify, then purify! If you can't purify, consider heating your dishes over a flame afterwards until they are dry and too hot to touch. That should kill most of organisms that would hurt you.

If you have absolutely no way to purify and no way to sterilize, then it's a crap shoot no matter what.

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    Yes, this is not a direct answer. IMO -- There's too much variance due to location to answer directly, and this is an important answer Commented May 13, 2013 at 19:07
  • I agree. We definitely should not imply that it's "the norm" to use untreated water for food, drink, or dish washing.
    – xpda
    Commented May 15, 2013 at 5:17
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    Regarding dishwashing (see original question), if I had to guess based on my small sample of personal observations, I would bet on the 'norm' being untreated water for dishwashing. ;)
    – ppl
    Commented May 16, 2013 at 2:55
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    99% of the dishwashing I have done (and seen done) uses untreated water. Frankly, who's going to filter/pump enough water to wash with? Put a few drops of bleach in your final rinse if you are concerned - but I'll bet the # of harmful water-living organisms that can survive a thorough drying on non-porous dishes is pretty low.
    – Lost
    Commented May 20, 2013 at 7:06

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