Drinking water: Is it clean? How clean is clean? How clean is too clean?
June 9, 2011 7:32 AM   Subscribe

So, I'm thinking about getting a reverse osmosis water filter for my kitchen sink but have some questions. Is revese osmosis the appropriate technology to address my concerns? Is demineralized water safe, especially for children? Can you recommend a particular filter or brand?

According to the "consumer confidence report" (PDF) from our water provider, there were no contaminants that violated the legal limits in our drinking water for 2010. However, according to the Environmental Working Group, for the years 2004 to 2007, 27 chemicals were found, compared to the national average of 8, and 16 of these chemicals were found to exceed federal or state health guidelines (compared to national average of 4). Chemicals in the latter group include uranium, radium 226/228, copper, lead, and arsenic. I have difficulty understanding the relative danger of these chemicals at the levels observed, but they sound bad!

I am also concerned that many relevant chemicals are not currently being monitored, or are being monitored in a way that minimizes the chance that potentially risky levels would result in violations. For example: chromium-6 is measured in aggregate with other forms of chromium that are much less likely to be of concern; the running annual average levels of atrazine may fall below the legal limit even though the chemical may exist at very high levels in the water supply during certain months of the year. I understand there are proposals to regulate an additional 16 chemicals in the coming years.

For the last year, we have been using a faucet-mounted PUR filter. But the replacement cartridges I bought don't seem to work. The water does not seem to be going through the filter, and the replace-filter light remains illuminated. It is a cheap piece of equipment and I have little confidence in it. It seems that a multi-stage filter including reverse osmosis is the best way to reduce the greatest number of these contaminants. However, I have read a few things, like this one (PDF) from the WHO, suggesting that reverse osmosis (and other water purification techniques that result in extreme mineral reduction) may not be healthy, either by depriving the drinker of helpful minerals or even by leaching minerals and salts from the body. This could be especially troubling for a growing child, and I have one.

1. Am I correct that filtering methods less extreme than reverse osmosis are not likely to cover the range of chemicals of potential concern?

2. Are the concerns about demineralized water serious? If so, would adding some minerals back be a reasonable way to address this problem?

3. Can you recommend a reverse osmosis system or provider? Some that I have come across include these: Omnipure Q 363, Apec RO-45, Trionics, and Watts.

Most of the information I have found is basically marketing material, including forums and review sites dominated by water filter salespersons with an interest in promoting fear about water quality and maximal solutions to the problem.
posted by nequalsone to Home & Garden (7 answers total) 3 users marked this as a favorite
The EWG is doing their best to scare people to improve regulation. This is good for overall regulation, but bad for making people worry about their water. Overall, the risk from drinking water in the US is Much Less than food and other environmental exposures - we often see levels of contaminants like perchlorate that are a lot higher in produce than are allowed in water, or levels of persistent chemicals in even organic eggs that are higher than allowed in water. This doesn't mean you should be scared of your food, it just means that your drinking water is pretty dang safe, and so spending a lot of money on a filter may not decrease your risks appreciably.

Not even looking at your CCR, your water sounds good, and I would drink it (I drink my public water without a filter, having worked in drinking water protection for years, because we have similar good CCR numbers). Most "emerging" contaminants are found at really low levels, but being extra safe is totally understandable with a kid. A filter isn't a Bad idea, as long as it's properly maintained to prevent mold and other growth.

1. Something as simple as charcoal filter (Brita, probably the PUR) will filter out Most contaminants of concern - honestly, I worry most about things like disinfection byproducts (THMs) and lead, and they are removed by a simple charcoal filter. Less extreme filtering methods are great for your situation.

2. I don't know about the demineralized water - my folks have reverse osmosis for their iron-rich well water, and have never mentioned it. I'd guess that there are other sources, as trace minerals in water vary so greatly by region. My daily vitamin includes minerals, too, so it seems like it'd be addressable.

And, yeah, don't listen to the fear-mongering of the providers - you're right, they're just trying to sell you a filter. If I were you, I'd go with a charcoal filter to add some peace of mind, but the reality is that adding a reverse-osmosis system is Way overkill for your pretty great drinking water.
posted by ldthomps at 8:42 AM on June 9, 2011 [4 favorites]

I use an Omnipure, but only for drinking water and water that is going INTO a recipe. (For pasta, cleaning, cooking items that use the water as a heat transfer medium, I just use tap water.)

The RO unit I have has 5 stages of filtering. I am surprised any water gets through, to tell the truth. Coupled with a house-wide sediment filter, what starts out as already pretty clean water ends up more or less like recently oxidized hydrogen.

Why? I can afford it, and it makes me feel good.

In reality, probably unnecessary. I live in a world where I breathe outgassing of plastics, hydrocarbons, sub-micron particulates, and I eat pesticide residue. My diet, while pristine in North American terms, has material of uncertain origin and unverified quality. I get petrochemical lubricants on my hands, marble dust in my nose, sawdust and solder in my teeth. I handle copper, aluminum, and zinc. My food comes in plastic containers. Even if I drank water directly from Heaven, every now and then I'd have to use a water fountain at the library. At 57, the evil things I INTENTIONALLY have put in my body have daily meetings to decide how they are going to kill me and/or make me unhappy.

You can nitpick life to death, and spend a lot of time worrying about perfection. It's the enemy of the good, as they say. Sane people optimize (i.e., trade off competing probabilities.)

An RO unit is fairly cheap, lasts a long time, and will probably not add a week to your kids' lives. I bought mine based on price and expected usage volumes and replace the filters at twice the recommended interval.
posted by FauxScot at 8:55 AM on June 9, 2011 [2 favorites]

I am not a chemist, but I can say that we have very hard water (old apartment). We bought this Pur dispenser for the fridge, which gets replenished on a daily basis. The filter is replaced about every three months. I can't testify as to what particular things are filtered out, but Pur claims it does pull out all number of toxins, and the water certainly tastes better than tap.
posted by Gilbert at 9:14 AM on June 9, 2011

"either by depriving the drinker of helpful minerals or even by leaching minerals and salts from the body."

I can't really answer the rest of this, but how hard is your water? In general, hard water -- which has a lot of magnesium and calcium -- is good for teeth and bones. Soft water may (may) have more sodium (softened water almost certainly does, since sodium is used in the softening, usually); it lacks the benefits of the "good" minerals and may add sodium to an already high-sodium diet. (As most American diets are.) I believe these health differences are pretty minor, if one's diet is otherwise healthy, but IANAD.

The other thing that raises concern where I am, which is an area with very hard, mineraly water (but very safe and clean), which has a distinctive taste from the tap (personally I like it -- and if this were Europe we'd bottle and sell it for its lovely distinctive terroir and its high mineral content and distinctive taste would both be considered benefits -- but Americans are weird about their water having any taste), is that a lot of parents buy those big workplace watercooler jugs of water delivered (from various local companies that make good money on people being weird about tap water taste), and that water is frequently not fluoridated. I don't know if filtering removes fluoride or not, but I'd find out; dentists and pediatricians around here now see young children of the upper middle class with rotten teeth because they only drink bottled, unfluoridated water and their parents don't realize they have to replace the fluoride in the child's life if they remove fluoridated water.

(I guess that's the sign of a super-successful public health campaign, when it's SO successful people completely forget that it's there.)
posted by Eyebrows McGee at 9:28 AM on June 9, 2011

Response by poster: Our water has a range of 104-282 calcium carbonate ppm. Obviously that is is huge range. The consumer confidence report does not give a median or mean, but I guess that means it varies from moderately hard to very, very hard. I never thought of it as particularly hard but I just realized that the slimy feeling in the shower that I associate with hard water is from water softeners, not hard water itself. Our water is unflouridated so we use flouride drops for our child.

I hate the PUR filter because it is basically crap, but maybe I should be considering a better-build-quality carbon filter, either faucet mounted, under the sink, or on countertop. (I always used a filtered pitcher in the past, but the additon of one small person has a disproportionate impact on the fridge real estate dynamic.)
posted by nequalsone at 10:03 AM on June 9, 2011

RO water is not dangerous in any way for drinking (there`s the wahoo fringe, but...). It is very, very similar to the distilled water in jugs at the grocery store, if you want to see what it`s like. Some, maybe even most of that is RO water. The usual complaints are that it`s tasteless and flat.

I would be concerned about exceedences of heavy metals, especially for radon. You don`t need full on RO (the expensive, gold-plated solution) to remove metals. A good activated charcoal system will do metals just fine. The Brita-type filters sorta work, but with water as hard as yours, they are going to need replacing often. It`s really hard to advise without actually testing the water to see. You might find if you can get water testing done through your state or municipality. Mine will do a limited amount for each consumer for $5/sample. Commercial labs will be able to do water contaminant analysis for $25 to $50/sample depending on how detailed you want it.

There are several levels of permanent installation. A version like this will probably do what you want. It can be installed on the house supply, but can also be put on a single tap. It has two filters in it, a pre-filter which removes muck and dirt, then the chemical activated carbon filter to remove dissolved chemicals and metal salts. Post install, you will need to changed the two filter cartridges every 3 to 6 months (depending on how dirty your water is and how much goes through it), for $20 to $30 per change.

A step up is a couple of big cylinders in the basement with a prefilter system like the one above. This essentially is just a big version of the carbon filter and can knock the contaminant levels down even further---longer contact time in the filter, more removed. My parents have a system like this. It cost several thousand to install and is about $1000/yr to maintain, but it's essential to mom's grow-op.

The RO system is one better than even that. Single tap units run in the $500 to $1000 dollar range to install, with whole house systems also going for thousands. Regular filter changes can be expensive as well, more than the activated charcoal systems. They also have power requirements for the high-pressure pumps and can be fragile or temperamental, particularly if the water is dirty, in my experience. Kind of like a pool, there's a lot you have to do with (some of) the systems. We chlorine flush our work system ever few weeks, for instance.

I'd start with a whole-house double filter system, the first option, testing the water before and after. It sounds like you already have pretty clean water, but this would add that extra level of safety for those uncommon, but annual, exceedences you have. This is still going to cost a fair bit, and require routine maintenance, but I don't think you need the really pure water the more expensive system will give you either as my mom does for her orchids.
posted by bonehead at 1:49 PM on June 9, 2011 [1 favorite]

Assume that your water is at the top of the calcium range. Assume that you drink quite a bit of it (3 liters/day), note that 1 liter of water is 1 kilogram (2.2 pounds). Assume that you're getting all the calcium out of the calcium carbonate (40%, by weight).

(282 / 1 million) * (3 kilograms) * (40%) = 338.4 milligrams

This is equivalent to a cup of milk or one Tums tablet, either of which is going to be more pleasurable than drinking that much water.

(I don't think you need to filter your water, but the trace minerals are highly overrated as long as you continue to eat food.)
posted by anaelith at 7:21 PM on June 9, 2011

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