Ann Arbor’s municipal water supply has been under threat of pollution for a while now:
For many years, a dioxane plume has been slowly creeping across town and contaminating municipal and private wells. The city has been monitoring and attempting to remediate (pumping out ground water, cleaning it, and pumping it back down ahead of the plume), but the plume is continuing its slow march toward the Huron River and Barton Pond on the north side, where the city gets 85% of its water.
In more recent years, PFAS/PFOS has been showing up in the Huron River and Barton Pond in higher and higher concentrations. The city has been adding filtration to remove that stuff before sending it out to customers, but there have been a few months where the concentrations (after filtration) were higher than their target.
And a couple of weeks ago, a chrome-plating company in suburban Detroit dumped 10,000 gallons of wastewater containing 5% hexavalent chrome into their city’s sanitary sewer system, where it ultimately ended up in the Huron River. If hexavalent chrome sounds familiar, it’s the stuff that made Erin Brockovich famous. Estimates of the total amount of chrome released to the river have recently been revised far downward (to just 20 pounds), but chromium-6 is nasty stuff even in very small amounts, and it will eventually reach Barton Pond here in Ann Arbor. Hoping the city will adequately monitor outgoing water quality and add filtration as needed to keep chrome concentrations in city water very low, but I’d rather not put my safety completely in their hands. I have memories of growing up in a northern Minneapolis suburb in the early 1980s, where we were suddenly told to stop drinking tap water because of a major trichloroethylene contamination problem. This was only after that contaminated water had been sent out to customers for a while.
My wife and I can handle showering and brushing my teeth with tap water, but for the primary source of water for drinking and cooking, we’d like an added layer of insurance in case the city slips up and sends dirty water out to us. From what I’ve been reading, the only technology that can really strip chrome out of water is reverse osmosis (RO). So now we’re looking at undersink RO systems for drinking water. Anyone have experience with them? Any concerns/regrets/suggestions?
We had a RO system when my husband had his saltwater aquarium. We had it set up to fill its own holding tank. So while the process was slow, once the tank was filled, it wasn’t a huge hassle to keep it filled - there was water to use while it refilled. And we always made sure to have a supply of replacement filters on hand.
You can get booster pumps for them. My booster pump roughly doubles how fast it makes RO water and at the same time, approximately halves the amount of waste water as the pump uses the high pressure it creates to force the water through the membrane.
You’d almost certainly want to fill up containers to stay ahead of it or you’ll never keep up. If I was going that route, I’d get 2 five gallon beverage dispensers of some sort. Fill both of them, then as soon as one empties refill it while using the other. You almost certainly won’t go through the full one in the few hours that it takes to refill the empty one, but you also don’t want to be sitting there with your drinking glass waiting for more water at that rate.
If you want to know if whatever filter you’re looking at is doing what you want it to do, you can get an ICP test done on the tap water and the filtered water.
IIRC, ICP tests, at least the ones I’ve had done, test for Cromium.
Here’s one of commonly used ICP test companies, at least within the marine aquarium world.
ETA: keep in mind that if you’re going to filter water for drinking, you’ll want to use that same filtered water for ice as well. Seems like that could be an easy thing to forget if you have an ice maker.
We’re on well water, which is perfectly fine to drink but a little unpleasant tasting, and our house came with a RO system. We had to replace it about 6 years ago when a seal failed and the old one started flooding out our under-sink area. Now the new one seems to not be filling the holding tank completely-- it’s about a gallon and a half and it seems to dispense less than half of that before it runs out and has to refilter a new batch of water (which as mentioned takes a long time). But we do use it a lot, and it’s also hooked up to our fridge so we can get cold water and pure ice.
Pro:
It does filter the water very well. I’ve never had it tested like you might want to, to make sure it’s filtering chrome and other chemicals you’re worried about, but it tastes like pure water, in other words, no taste at all. In fact it might be off-putting to some (I know bottled water adds minerals so it still has a bit of a flavor) but we’re used to it.
Cons:
You’ll probably want a plumber to install it, unless you’re pretty handy.
The filters aren’t cheap, and have to be replaced every 6 months or so (for the pre-and-post filters; the actual RO filter I’ve heard only needs replacing every year or so, or even longer, depending on what the water’s filtering).
As mentioned, it takes a while to refill once it’s empty. Depending on how much drinking water you go through, you’ll probably want to keep bottled waters on hand for the times you empty the RO holding tank and need to wait.
Pro tip:
The RO system has 3 filters: a pre-filter, which takes out the worst of the solid contaminants, the RO filter in the middle, and the post-filter, which catches whatever the first 2 don’t, which isn’t much. So when you need to replace the pre and post filters, you can use the old post filter (which will be almost pristine) to replace the pre filter, and only replace the post-filter. Save some $$.
The system I’m looking at ranks highly in a lot of reviews. The wastewater ratio is 3, i.e. three gallons of brine down the drain for every gallon of filtered water delivered. Which seems high, but for the amount of water we drink and cook with in a day, the brine is equivalent to showering for an extra minute each.
Most/all of the undersink RO systems that don’t use a pump feature a multi-gallon accumulator tank. The system I linked to above will produce a gallon in about 30 minutes of continuous operation, but it looks like the accumulator can deliver a couple of gallons of already-filtered water in just a minute or two.
You can have a pressure tank in an RO system, so you can store and use water more quickly than the filter produces it.
In RO systems for aquariums, Bulk Reef Supply (who wanted to sell folks a second membrane) found that a second membrane would filter the brine adequately, and provide about twice the output of a single membrane. I don’t know if that would be suitable for potable water.
I was asking my parents about their RO system. The last stage in their setup puts some minerals back, to improve the taste.
Is this really a thing?
I too am thinking about installing an RO system this fall. The water here is super hard and probably contaminated with all sorts of chemicals, seeing as we live near agricultural fields. The neighbors–not to mention the previous occupants of this house–used all sorts of chemicals locally, including weed killers (roundup, etc.).
We had a Rainsoft RO under-sink system for over 20 years, and the water tasted so much better than city water, it had a five gallon storage tank, so it could meet all our needs, except for filling the ten gallon fish tank. Over time the bladder would need attention, deflating and inflating to keep the water pressure up. The filter replacement process was a bit of a pain, the housings would get very tight and hard to unscrew, and every week you were supposed to drain the tank, do a five minute flush, and then let it refill, so it did use a lot of water.
A couple of years ago, we replaced it with a Culligan under-sink RO system. This has been easier to maintain, filters are super-easy to swap (once a year), and no flushing is needed. Same five gallon capacity. The only annoyance with this one is after you run the water, e.g. to fill a glass, you heard the trickling of water in the system until the tank is full. At first we thought something was leaking, but I believe it is just the drain.
They are not cheap, but we will never go back to regular tap water (at least in our current city).
Thanks for everyone’s input so far. What’s anyone’s experience with/concern regarding the potential for bacterial growth downstream of the RO system, particularly in the accumulator tank where water is stored? Anyone had any issues with this? Multiple sources indicate that RO systems are quite good at filtering out bacteria, but of course there may be some that are in the tank and fittings when you first assemble them.
Do you sanitize your RO system on a regular basis?
Aquarium RO filters add a dionozation (sp) stage. Is this done with potable water filters? It is rumored that aquarium RO water does not contain some elements essential to life.
No direct experience with them - though I wish they’d been available when I was growing up: our house had well water, and water softener, and the tap water tasted bad.
If you just need drinking / cooking water, getting water delivered (in 5 gallon jugs) might be an option. I have no idea what the cost is versus a RO , and you’d want a stand to mount it in.
Follow up: I just installed the RO system as planned. The water is indeed well filtered, with a total dissolved solids measurement of about 35, compared to my previous setup (two PUR filters in series, TDS = 250). The alkalinity level is raised by the last stage of the 6-stage system to improve the taste; I suspect this raises the TDS number up from near zero.
It has a ~5 gallon tank, from which most of the pressurized water emerges when I turn on the tap. It’s a fairly low pressure system, with just enough inlet pressure to function (about 45 psi); no booster pumps needed, apparently.
Question: The water, when it emerges from the tap, has a lot of very fine bubbles in it. These form a cloud in the water glass or pitcher, which clears from the bottom up. Is this always a thing with RO systems, or do these bubbles eventually go away?
Also, this morning, after it sat overnight and the system fully filled the tank for the first time, I filled a pitcher of water to about 1-2 quarts. When I turned off the tap, I heard a shuddering / vibration noise coming from the RO filter area, lasting a few seconds. What could this have been?
In my experience, that cloudy/bubbliness goes away after the filter material has had a few changes of after run through it. I recall my instructions said to run a few gallons through the system first.
The shuddering is probably just the system repressurizing after letting off a volume of water. Mine makes noise at that point as I have a passive pump that kicks in during refill.