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Thoughts/Comments on RO (Reverse Osmosis) water systems

12 years ago

Just wondering if anyone has any thoughts or comments on RO (Reverse Osmosis) water filtration systems. As part of our kitchen remodel DW and I are moving from in the door water on the fridge to an dedicate sink faucet. We are not sure yet if we are going to go with a simple in-line water filer or an RO system.

As I posted in another thread my main holdup with the RO system is the amount of waste water it produces, here is a quote I have read often online:

"An RO unit delivering 5 gallons of treated water per day may discharge anywhere between 20 upwards of 90 gallons of waste water per day. For household use, however, and based on consumption of half a gallon per day, this may amount to less than a toilet-flush per day."

Can anyone offer up some advice on this type of system for me.



Comments (28)

  • 12 years ago

    Zero Waste Reverse Osmosis System $290

    Here is a link that might be useful: Costco

  • 12 years ago

    Suggest re-posting at the plumbing forum.

    Your statement example of 4X - 18X waste water is inaccurate for any quality RO system. The worst come in about 4-5X. The best is Kinetico which is about 2X at 60psi...and is also among the most expensive. "Zero Waste" method pumps the waste water back into your system which avoids "waste" but brings other problems with it.

    What is it about your water supply that you want to change via filtering?

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  • 12 years ago

    Agreed, a simple one-RO-filter system should not waste more than 2/3 of the supplied water. This depends, however, on how the water is collected after the RO filter and how the intake to the filter is configured. It is best to have an automatic shut off on the intake, and a way to keep the output pressure at the RO diaphragm low, while supplying the RO water at high pressure to the faucets.

    A series setup is also possible, with two RO filters, This can reduce the waste ratio. Note that in addition to RO filters, one needs charcoal and particulate filters, depending on the water source.

    I use components from SpectraPure for this, including in particular a post filter peristaltic pump, but I'm sure that there are many other suppliers of appropriate systems.

    While the waste water may seem like a waste, it could be used for other purposes if collected. The mineral concentration will be only a little higher than that of the initial water. Also, the amount of RO water used per day is modest for most households.

    If your water source has unusual issues with chemicals or minerals, it is important to talk to a specialist at one of the RO supplier companies.


  • 12 years ago

    In my case, not only did I need the RO water for watering orchids, but my centrifugal humidifier using muni water would leave a layer of dust on everything, as the ultrafine particulates in the water (perhaps added by edict to make it alkaline) were left behind when the vapor evaporated.

    RO water also makes excellent tea free of spurious tastes.

    The purpose of the specialist suggestion was to choose the prefiltering appropriate to the water situation, not to decide whether RO water was needed.


  • 12 years ago

    We have an RO system under our kitchen sink with a 1.5 gallon holding tank. The system also has a peristaltic pump which makes the system process faster. With this system we supply a sink-side faucet and the water to our refrigerator icemaker.

    Why did we get an RO system? Our city water supply is hard water (central Indiana). We are iced tea drinkers year-round and our tea made with RO water is crystal clear and our ice does not have sediment. When we first moved to the Midwest and experienced its hard water, it took me a long time to figure out why my tea tasted so terrible and was cloudy. When hard water is boiled or heated to almost boiling like for tea or coffee, then cools, the minerals will precipitate, leaving your beverage cloudy.

    Having the RO system at my kitchen sink also allows me to have softened cold water supply at the kitchen, too, since I don't have to use that water for cooking. Softened water means the faucet o-rings and other parts last longer.

  • 12 years ago

    Thanks for all the replies, and a little more information on my as requested by a few on there.

    I live in the west burbs of Chicago, so water is actually pretty good. We are on Lake Michigan water, not a well or anything else. We worry about sediment and other things that are added to the water.

    Right now we just drink most if not all of our water from our fridge door and the in-line filter we have on it. But we are going to go with a Liebherr as part of our kitchen remodel and that does not have the water on the door which we don't want. So, this is moving the water to our sink and I am looking at the advantages/disadvantages of the RO vs IN-line systems. I like that the ROs remove a lot more than just standard in-line stuff, so that is why I was asking about the RO systems.

    I appreciate all the great info posted in here so far, this will and has helped me to make a better decision, though I am still not sold on anything yet at this point.


  • 12 years ago

    kaseki and nanj make my point for me. Specialized uses like orchids and humidifiers (and even being fussy about how your iced tea looks) are very different from just wanting good-tasting (i.e. no chlorine) water to drink and cook with.

    Phil, if you just want something that tastes similar to the filtered water from your fridge via a tap by the sink, go for sediment, carbon, and maybe carbon/metals filters instead of RO. There are a lot of filters out there. Unfortunately, many of them lock you into buying proprietary replacement cartridges from the same vendor. I know I cringe every time I order new Pur filters for our KA fridge- and my FIL's GE fridge had an even-smaller-but-more-expensive cartridge.

    The least expensive route is to put together a system yourself that uses standardized 2.5" x 10" cartridge filters. There are a lot of competitive sources for the filters then when you're ready to replace them.

    The link is a quick search result- you can see the most expensive carbon filter is still $40 less than the least expensive RO filter (excluding the Aqua Pure brand carbon filters, which have the whole expensive/proprietary thing going on). Fewer consumables, less water wasted down the drain (unless you're enterprising enough to collect it for some other use, which is doubtful for the majority of folks).

    Here is a link that might be useful: Filters @ Kleen Water

  • 12 years ago

    Thanks Thull, for us, thankfully, it is more about having something that we feel is better for us than something we need to have because our water is bad.

    Do we like the taste of the water from the fridge compared to the faucet, honestly it is not that much different, but we like that the filter at least should remove some things that might not be as good for us.

    I'll take a look over your link but I appreciate the suggestions and at this point I think we are leaning away from an RO system and toward a filter, though maybe I piece something together for myself that works for us.

    I appreciate all the feedback.

  • 12 years ago


    From what you've written lately, it seems to me going with RO likely overkill. A good full-flow sediment+activated carbon filter might fill the bill MUCH more cheaply if good taste and no sediment is all that's needed. Talking about a single-cartridge in-line filter and housing. Would require a not-too-difficult re-plumb under the sink but a good sized cartridge will give you six months of no chlorine and no sediment plus easy filter-change when the time comes.

    If you're already satisfied with the taste from your tiny refrig. filter, this would be like that only probably better plus full-flow.

  • 12 years ago

    One thing to know about RO water: The process can make the water more acidic, depending on its pre- and post-RO chemistry. Acidic water can (very slowly) leach some metals, such as lead if present, out of plumbing.

    RO systems should use inert polyethylene tubing with plastic fittings. John Guest type fitting configurations are ideal for easy assembly and disassembly.

    RO water should be tested for PH. While modern faucets should be reasonably safe, at least with flushing of standing water, acidic results imply a greater need for care in materials selection than alkaline results.


  • 12 years ago

    I have the RO system that deeageaux linked to. So far it has worked as advertised. It feeds a faucet at the sink and the ice maker in the freezer. The water tastes like, well, nothing.

    The "waste" water is fed back over to the hot side via a small pump. Since I have the DW and clothes washer on the same water line, that less-than-warm hot water gets used by those appliances with built-in water heating. I also have a half bath in-line so that water gets used for hand washing, in addition to being used at the kitchen sink. Keep in mind that it's not "waste" water as in dirty water. It's just water with high-levels of whatever got filtered out.

    It only uses a little bit of electricity via the transformer for the pump. It also has no impact on my water bill, since none of my water is going down the drain due the filtration system.

  • 11 years ago

    If you want best RO system then you can get it from them.

    Here is a link that might be useful: 250 lph ro

  • 11 years ago

    Instead of all the problems associated with RO, I recommend to my customers an Everpure filter system.
    They are a lot less hassle and no water wasting flushes like in an RO system. A lot of icemaker systems don't play well with some RO systems but they work ok with the everpure filter.

    Here is a link that might be useful: EverPure filters

  • 11 years ago

    "20 upwards of 90 gallons of waste water per day. For household use, however, and based on consumption of half a gallon per day, this may amount to less than a toilet-flush per day."

    Hmmmmmm, a 90 gallon toilet flush, whose Toto is that, the Green Giants?


  • 11 years ago

    I am not sure I buy the cost of ownership argument. I spend $40 a year on 3 cartridges for my RO system and get many hundreds of gallons of water out of it. If I tried that with a Brita water tank (like I do at my lakehouse), I would spend at least twice that on those silly carbon filters.
    Yes, I use a lot of RO water in my ice makers, ice tea, hot water dispenser, coffee maker, and most importantly my saltwater fish tanks which require a no-phosphorus water to mix with salt. My water is softened first which helps the life of my 5 stage system. I have a 3/8th inch polypropylene plumbing network running throughout my mainfloor kitchen and downstairs bar.
    I would also argue that an RO system is better for the environment than bottled water any day. I will admit a carbon filter system may be the best for the environment, but cannot achieve the same results for multiple demands.

  • 11 years ago

    We had a Culligan RO system for several years, in our previous house we sold in 1994. Things have probably changed since then and improved, but here goes...

    Ours was a 2-gal tank and took hours to fill. If the tank was emptied between cooking and other heavy demand, I had to wait forever or else draw water a day ahead, like when we were having a dinner party.

    The filters were terribly expensive to replace. We had a whole-house water softener system and were told that helped the filters last longer.

    At our current house, we opted for a Brita filter pitcher and have been happy with it. Our current refrigerator also has a built-in filter for the water dispenser.


  • 11 years ago

    If you use a lot of water, buy a bigger tank. You will generally get better water pressure from a bigger tank as well. It will refill overnight if you buy a reasonably fastsystem. I have an APEC system (actually rebought another when we moved) and am pleased. Make sure you get the "permeate pump" as an option as it helps to get more water into your tank which allows for more storage, and generates more pressure. I am under the impression many brands are similar.
    Most of the current setups have a cotton first filter, a carbon second filter (or two), the RO filter, and then some have a "polishing" carbon filter after the tank and before your faucet.
    It costs me $39 to replace the cotton filter and two carbon pre-filters yearly. The RO and polishing filter need to be replaced every 5-7 years at a cost of $70.

  • 11 years ago

    One of my sisters has a backyard greenhouse and at least a dozen orchids growing in it (she's a cert. master gardener) among other fancy plants. They use our local tap water, approx. 4 grains of hard/softness and don't filter it..

    Something else to research regarding RO as your primary drinking water supply, is the minerals depletion. IIRC, our old system mentioned above filtered out all the minerals including the good ones. Years of drinking RO water could leave a person with some level of mineral deficiency. I am no expert, but had read that somewhere.

    I was always sure to take extra calcium & supplements when we had that RO system. It was long before Brita filter pitchers came along, and our incoming water pipes were galvanized pipes and full of rust and chlorine. RO was a better solution for us on *that* water supply, but the lack of minerals (like drinking distilled?) was always a concern for me.
    That was 20+ years ago, so you might want to research it, as the info may have been proved incorrect by now.

  • 11 years ago

    Just as an update since people are posting to this we did not go with a RO system at all. We have a set of pre-filters that go in to a Ionizing system. So far we love this system, my wife has problems with heart burn all the time and this has seemed to really keep things in check. Not saying it still doesn't occur, but it happens less often for her and is not as painful.

    This system is not for everyone and isn't cheap, but we love it so far.

    We went with this unit:

    These units also have filters inside of them, so the pre-filters are in addition to what the internal filters do. We don't have very hard water in my area so that was not a concern.

    Again, so far we have loved this unit. We put it in on a temp basis before our remodel and were using it for a month or a little more and then had to take it out for the entire remodel (3-4 months). My wife really noticed the difference in not being able to drink this water every day. Since it has been put back in her heart burn symptoms have gone back down again, they were horrible while we did not have this in.


    This post was edited by philwojo99 on Thu, Apr 11, 13 at 12:10

  • 11 years ago

    Ionizing water and filtering it are completely different animals. Ionizing it will use electricity to skew the balance of hydrogen ions in water. It is not at all clear how this will benefit someones health as no real, large randomized studies have been done, or will be done. Might alter the taste, and if you like it, great. If you think it has helped your health then definitely stick with it.

    RO systems remove minerals, bacteria and all particles bigger than water (OK most). If you rely on tap water for your nutritive needs, and not your hydration needs, then you need a better balance to your foods. Fluoride is one example that might be hard to get in a diet, tis why they add it to water. As an alternate I brush my teeth. I also use tap water to boil pasta and potatoes, which is another way to get fluoride. Tea, saltwater fishes, etc etc. all with fluoride. Of course too much hurts your thyroid.
    If you want to poor a glass of water that tastes good, get a britta filter. If you want to make clear ice too, maybe a filter in your fridge. If you drink A LOT of water, or have a family who loves ice (as in a dedicated ice maker), or want clear tea, or have delicate pets/plants, then RO water makes more sense.

  • 11 years ago

    See link below

    Here is a link that might be useful: Wikipedia article on water ionizers

  • 11 years ago

    First off, like said above, many systems do not waste as much water as you described, and most systems are 1:2 or 1:3, mine of which is a 1:1 ratio. Wherever you got that information must have been from someone trying to direct someone to buy something other that reverse osmosis.

    Second, it was suggested above that you do not need reverse osmosis. There are too many chemicals in our water to even suggest a regular filter would suffice. The EPA has even stated that there are over 80,000 chemicals and toxins, with more than 2,000 more being created each year, in which most of the 80,000 have made it into the water supply at one time or another. And reverse osmosis is the only system proven to remove pharmaceuticals, even though some water filter companies suggest they remove them, this hasn't been proven and is a marketing scam.

    I myself had done a lot of research before making my purchase, and reviewed about 30 companies and hundreds of models. I ended up purchasing a system from Aquasafe Systems which I felt was the best purchase I could make, as the filter replacements were inexpensive compared to the rest, and are standard size in case I needed some in a hurry, I could go to the local store for a quick fix. My system also didn't come with unnecessary stages like UV, which are rendered useless with the carbon stages, but did come with a DI resin stage to ensure alkaline water between 7.5 and 8.5 pH, which was an important factor to me.

    Here is a link that might be useful: Aquasafe Systems

  • 11 years ago

    As someone well steeped in a medical and science background, I can't really recommend an ionized water system over RO. No offense.
    Of course all unstudied things remain a mystery, but sometimes there are reasons we don't study things, because they don't make a lot of sense. Water is an extraordinarily weak buffer. You can sway its pH by electrolysis, but upon contact with any small amount of acid or base, it will quickly lose whatever pH it has. Read, stomach acid vs ionized water... stomach acid wins.
    If your goal is better tasting water, then carbon may be fine. If you want to remove tasteless chemicals and toxins, maybe RO is for you.
    The claim that there are 80,000 chemicals and toxins in the water supply at one time or another is sort of like claiming that every once in a while somebody gets hit by a bus, or struck by lighting. Yes, they are very real things, like chemicals in water, that may cause harm. But living your life in fear of such things can make people do extreme things, and waste a lot of money. You are not going to stay in your house, and avoid all roads to avoid lighting and buses, nor should every house install an RO system "to be safe." If your city has a bad track record for maintaining its water, you live near a clearly unregulated pesticide production facility, or you live on a farm with a well that has fluctuating water quality, it may be that an RO system is for you for "safety reasons." I still maintain an RO system is for us water snobs that not only want better tasting water, but clear ice, clear tea, and better water for our plants and high maintenance fish....

  • 8 years ago

    I have never owned an in-home RO unit. But I did work in a lab that substituted RO water for distilled water uses. We had regular serious problems with our commercial RO unit until we installed a water softener upstream. It could not handle water hardness well and stopped up. It also created a lot of waste water trying. This was about 25 years ago and I know progress must have occurred. We personally use a 1 micron prefilter on our whole indoor house water to protect hot water tanks and valves. We have a dedicated line to our cold water tap in the kitchen which also feeds the refrigerator water dispenser. It uses a whole house charcoal element. The water tastes great. Our city water is pretty soft because it comes from the Columbia River and is melted snowpack.

  • 4 years ago

    We run UV plus the Carbon to try to eliminate chloramines as much as possible without having to use meta. We run a tight sediment filter - 5 micron - before the UV just to ensure maximum effectiveness. As soon as we see any change on the test strip, we change carbon tanks. We are on muni - but we do pick up some sediment and particulate. We are in a pretty urbanized area outside of NYC - so VOC and other contaminant is always on our mind. Chalk it up to being obsessive more than anything else.

  • 4 years ago
    last modified: 4 years ago

    For RO, what starts out as 1:4 increases dramatically as the Back pressure from the storage tank increases, leading to poorer performance. If you want the most efficient RO, you want high source pressure (or a booster pump), an automatic shutoff valve that shuts at 2/3 capacity, and even better a permeate pump.

    I have a well and septic, so I am not really wasting water. I do have a softener, so I am putting more salt in the ground though. I use KCl instead of NaCl, which is better, and can be used by plants.

  • 4 years ago

    Correction to a mistaken statement I made 7 years ago. The permeate pump I used then (aquatec ERP 1000) and the pumps I use now (2X aquatec ERP 500 -- much quieter) are not peristaltic pumps. They have a more complex mechanical operating principle. (See diagram under magnifying glass.)