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Comment by dangoor | Hacker News Reader

Does anyone have opinions (or even knowledge of actually reliable data) about whether drinking water filtered with reverse osmosis is worse for you than drinking tap water with PFAS, etc? I've seen the argument made that RO water is worse because of mineral loss and that the little remineralizer cartridges and such don't do enough to replace the loss.

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I struggle with concerns about mineral depletion when you have 50%+ of your diet which is solid that probably contain a similar proportion of minerals to the water you consume.

Was about to comment the same thing. Constantly consuming solids and liquids from other places that contain all sorts of minerals, I highly doubt I'll be depleted because of my RO system.

More of a concern to me is that it's almost certain that PFAs etc are contaminating those other sources of food.

Quite a few hog and poultry farms are downstream the Cape Fear River from the Chemours plant.

Also, all those RO systems run the water through an enormous amount of plastic, and store the filtered water in a rubber bladder.

When looking into this previously my decision was to avoid introducing yet another potential source of contamination.

This is for sure a concern. Also when my RO system was first installed, the filter instruction said to run it to fully empty twice to run out the detergents (?) that the filters came with? I have to wonder what's in that, or lubricants used in construction.

I would not be surprised to find PFAs used somewhere in the construction of the system. Under regulation of this stuff means it's everywhere.

But then again, lots of the pipes, fixtures, etc. in the house ... plastic etc. as well.

Yeah the rubber bladder always concerned me as well. They say it is made of butyl so leaching is not to be expected but what if the production biproducts left on the inner surface are leaching out over time.

Same goes for a random o-ring or the PTFA tubing.

I have a TDS measurement device but these are questions beyond total dissolved solids.

I actually have a countertop RO system that puts the filtered water directly into a glass jar. The filtration system itself is certainly plastic.

The anecdote I have is that one of my grand daughter's teeth are worse than my other grand children and grand nieces and nephews. She used RO water more than the others when she was younger, and her dentist reinforced the idea that RO water was unfriendly to early tooth health, apparently due to reduced fluoridation. I'm not suggesting that is worse than forever chemicals.

I’m dubious. Millions of people in the country are on wells and don’t use any fluoride, also fluoride isn’t present in every municipal drinking water supply.

The things I've read about fluoridation make it sound like fluoride applied to the surfaces of the teeth (eg via brushing) has the most benefit. I have to wonder if your grand daughter was also using a non-fluoride toothpaste.

You can get your mineral levels tested... just drink RO water for a month and do some blood work. You will feel better

Serum mineral levels are not super useful because many minerals are stored in bones and tissue.

Before they are stored there, they are taken there via blood

If I want to take stock of my available goods, do I count how much cargo vans going in and out of the warehouse are carrying, or do I have to go inside and take a look at what’s actually in store?

Tap water, like blood, is a flow not a stock

We don’t need minerals for blood (hardly any consumers there), but for tissue and structure. Those sites store and don’t flow.

Last I looked into this, it seems there's products out there now that offer "nanofiltration" which has more permeable membranes than RO filters so the minerals can pass through but the more complicated molecules like PFAS cannot.

Nanofiltration is going to leave in things like lead, etc which makes sense when you think about how it's leaving in other ions like salts etc.

In fact it will leave in not only metal ions, but pesticides and antibiotics too.

More info here https://aquaclearllc.com/technical-info/reverse-osmosis-vs-n....

It's a hot topic. I see lots of people drinking RO water and not dying, so at least in the short-medium term its fine.

My conclusion of all my research was "I feel safer drinking RO water compared to my cities crappy tap water"

> I see lots of people drinking RO water and not dying

This also holds true for water with dangerously high levels of lead, and even the PFAS which are driving people to RO in the first place. It's really a terrible measure of how safe something is.

We have proven science around what lead can do. We don’t have that with RO water. It’s very fuzzy and like “if you drink only RO water and no minerals this is how it’s maybe bad”… but leaving out stuff like the coffee you make with RO adds back junk.

I wonder how much of the plastic in the RO machine leaches stuff into the supposedly pure water. The same for one's household plumbing --- does it leach into the water?

Yah, this is totally a thing.

For example, https://awwa.onlinelibrary.wiley.com/doi/abs/10.5942/jawwa.2...

> RO water is worse because of mineral loss

This sounds like a woo natural health claim. Is drinking water really a significant source of minerals?

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