Should water that's been distilled through reverse osmosis taste this nasty?

December 16, 2008 11:51 PM

My workplace has a reverse osmosis water filter that produces a beverage tasting nothing short of pure evil. Why might this be?

Referring to previous posts about yucko-tasting water, I considered it being the glasses or my mouth or something, but everyone in the place except the boss (who I suspect is in payer's denial) agrees that the filtered water tastes off, and we're all using different glasses (several different types available here) and mouths. I'm not sure how to describe the taste.... drier... much, much harder. It leaves my tongue feeling like it's wearing a fuzzy sweater. Or needs a good shave.

I've drunk similarly filtered water in a different location (at the boss's house, so can probably assume it's the same filter/brand) and it's also tasted evil, so it probably isn't the location. It's not just this particular time, either: we're talking a period of a year here that it's tasted this way.

I don't know how the machine itself works so can't really guess at what could be transpiring inside. Could a criminally neglected filtering system cause this? Inside the section between machine and finished vessel of filtered evilness seems to be a baggie of what Googling reveals must be charcoal, but I haven't dug any deeper into its innards. The baggie looks, well, pretty black -- as charcoal might.

I wanted to poison myself LESS by starting to use the filtered water (they've recently introduced fluoride where I am, and I'm one of THOSE freaks), but fear I'm poisoning myself more imbibing this liquid atrocity. We've all expressed to the boss that we think it tastes like shi-...vermetimbers and we can't believe he prefers it, so you'd think if it was a filter-change it needed that he'd've performed it. So... is this just normal "reverse-osmosised" taste?

posted by springbound to Food & Drink (10 answers total)

So... is this just normal "reverse-osmosised" taste?
Yes. We have one of these machines on our boat for long trips and the water tastes very foul and dead. Demineralised water just tastes like this unfortunately.

I don't see how a failure of the machine could poison you, if the membrane is damaged you'll just get... unfiltered water.
Your precious bodily fluids are safe.
posted by atrazine at 12:54 AM on December 17, 2008

Best answer: It is a pretty counterintuitive situation. Basically, pure water and natural water aren't the same thing. Pure water doesn't exist in nature, since it usually has small but harmless (and oftentimes beneficial) concentrations of minerals and gases from the environment. So when you think of "pure spring water", that includes all the various trace elements that you'd expect water flowing over stone and soil and fish poo to have.

Filtered water, on the other hand, is... well, artificial. Moreso the more that it's filtered. Theoretically, perfectly pure water -- hydrogen, oxygen, and nothing else -- is the "cleanest", but to a human tongue evolved in the natural world it tastes plain and empty and unhealthy, like you described. So in all likelihood your filter is working too well.

The artificiality of pure filtered water is bad enough, in fact, that most of the big water bottling companies add in the trace minerals after reverse osmosis, to improve the mouthfeel. For instance, according to the infallible Wikipedia:

[In making Dasani,] Coca-Cola uses tap water from local municipal water supplies, filters it using the process of reverse osmosis and adds trace amounts of minerals, including magnesium sulfate (Epsom salt), potassium chloride (a sodium-free substitute for table salt), and common salt.

My advice? Either persuade your boss to get a filter that allows harmless mineral matter through (I don't have a lot of experience there). Or just bring your own bottled mineral water to work.
posted by Rhaomi at 1:25 AM on December 17, 2008 [1 favorite]

Another explanation of the science behind "pure water"

And a third recommendation: Get a water cooler! Aren't they required by Office Stereotype Law or something? (Assuming you work in an office, that is.)

If you do get a water cooler, make sure it's the kind that dispenses those little conical paper cups. They are Fun.
posted by Rhaomi at 1:36 AM on December 17, 2008

It's not just that the water is demineralized. It's also deoxygenated. Distilling, which doesn't do nearly as a good a job at deoxygenation as an RO filter, leaves water tasting harsh and flat because there's no air in it.

Try shaking it up for a minute or two before drinking. It won't make up for the lack of minerals, but freshening it up a bit ought to help.
posted by valkyryn at 4:43 AM on December 17, 2008

Water purifying machines and filters need to be cleaned every once in awhile. Just because there is potable water coming in and out doesn't mean that it will always be clean. Mold and algae can grow which can make the water taste bad.

Anyone with a Brita pitcher can tell you that it's a good idea to wash it out with soap and water every time you change the filter. The charcoal filters should be changed on a regular basis.
posted by JJ86 at 6:51 AM on December 17, 2008

Are you sure it's really reverse osmosis? Maybe they hooked it up backwards and you aren't getting the filtered water, you are really getting the unfiltered waste. Or the filtering membrane has failed.

I know this is just a matter of taste, but I find RO water to be delightful.
posted by gjc at 3:25 PM on December 17, 2008

Response by poster: Well ewwwww. That sucks.

Thanks though, guys, for the advice. I did try blowing air in it to the point of bubbles (my only viable option today for trying to reoxygenate it in the absence of a shaker!), and when that didn't work, tried pouring myself a half-half cocktail of distilled and tap water to see if that could be a solution, too; but it still all tastes pretty ratsh*t. Small business + crap economic times = not going to throw my weight around about a water cooler (different laws in Australia may prevail, too, but anyway there's certainly water available from taps and distiller that I imagine would satisfy legal requirements), and I'm trying to get away from drinking so many store-bought bottled bevvies as it is, so it looks like I might have to just give on one count or another. I will look into whether less enthusiastic filters are available that I could suggest, though - thanks Rhaomi for the idea.

Well, glad at least that I realised this sad state of affairs before spending any more time pondering buying a filter for home! Thanks everyone; I appreciate your help!
posted by springbound at 3:33 PM on December 17, 2008

Response by poster: gjc, ok, er, thanks, that grossed me out enough that I think now I'm going to take a better look inside the thing with the help of some online-acquired instruction book. ;) I'm so in disbelief that anyone could call this delightful that I'm open to believing I *could* be drinking filtered waste here. :s
posted by springbound at 3:38 PM on December 17, 2008

For what it's worth, if the bad taste is due to the missing minerals, you can add back some of them. I used to work in a kitchen with reverse-osmosis filtered water, and we always had a bottle of Concentrace mineral drops sitting by the faucet to add to our drinking water.
posted by not me at 7:45 PM on December 17, 2008 [1 favorite]

Response by poster: Thank you, not me -- I had no idea such things existed! Will definitely try and get my hands on it and give it a go. It ain't that the machine's in need of cleaning or put together wrong, so I'm guessing it really is just foul-tasting as a result of being distilled.

Thanks again!
posted by springbound at 6:52 AM on December 20, 2008