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Thread: Reverse Osmosis Systems

  1. #1
    Californian in DC DrWurm's Avatar
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    Reverse Osmosis Systems

    I'm not planning on getting one any time soon, but I do want to learn a little bit about them. In the long run, I'm sure any RO system would easily be more cost effective than weekly CVS trips for gallons of distilled, but I don't get what exactly differentiates one system from another.I've seen counter-top filters for less than a 100 dollars, and under-counter systems around 400 dollars.

    What's the difference in the water that comes out? What should I look for in a system? What's the best? What's good enough (for CPs)? What should be avoided?

    Jason

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    mark.ca's Avatar
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    I got on of ebay for under 90$ and in 4 months it already paid
    off for itself. They said it's a 0ppm filter but i never got under 10 ...or over 17, wich is fine with me and my plants.
    Best regards,
    Marius

    My Website: http://droseragemmae.com/

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    feedme's Avatar
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    I also got mine on ebay. I got a 5 stage RO for around $120, but it will pay for itself in a few months. It keeps the water around 2-5 ppm.

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    Tony Paroubek's Avatar
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    Basic rundown on RO systems.

    Each filter part is called a stage.

    Prefilters - filter the water before the RO membrane. Usually there is a sediment filter for particles. Also usually a Carbon filter to remove mainly chlorines which will eat the RO membrane. The better systems use a separate particle filter and a carbon block. Cheaper systems may use a combination filter that catchs particles and does carbon filtering all in one. (they usually are less effective and need to be replaced more frequently)

    RO membrance several different types but the most common is a TFC (thin film composite) membrane. These days they are all decent and should give you very high quality water. The question is how much do you need? They are rated by how much filtered water you will get from them over a 24hr period running the filter. The higher the output the higher the $$. Keep in mind though that they are tested at a high water pressure and certain water temperature, usually 70 degrees f. IF your water pressure is low and/or your water temperature is colder, you will get less purified water out of the filter. So generally it is better to get an oversized one because most people don't have the water pressure and temperature to get the rated output.

    Post filter - a filter that polishs the purified water from the RO membrane. Sometimes these are additional carbon filters, sometimes they are mix bed deionizing beds etc.. Way overkill for anyone needing water to use on their plants. A properly working TFC RO membrane should remove 98% of the dissolved solids in your water, without additional post filters.

    Other things to consider:
    It takes roughly 4 gallons of water to get one gallon of purified water. IE 3 gallons go down the drain while 1 is purified. If you pay alot for water a RO system may not save you all that much if you have access to cheap RO water from the supermarket or something. Don't forget to factor in the cost of replacing prefilters. Particularly the carbon block, which yyou should always get a quality one and replace it a couple times a year. If not you risk punching holes in the RO membrane from chlorines added by municipal water companies.

    Look for at least a 3 stage system. One particle prefilter, One carbon block prefilter and the RO membrane. You may find systems with post filters but I wouldn't spend extra for them.


    oh yeah.. you also want a system that has standard size filter housings so that you can shop around for filter replacements and not get stuck having to buy a certain filter. This would also allow you to replace your RO membrane at a later date should you need more output or to replace it when it water quality decreases over time.
    Is that a Nepenthes in your pocket or you just happy to see me?

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    sea bear returns! theyellowdart's Avatar
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    I would spend a little extra money and get an RO/DI system instead of plain RO if your tap water sucks. The added deionization(?) stage removes all the impurities that that RO leaves behind.
    But... If your tap water is very good quality, you could probably save a few bucks and just get the RO.
    growlist

    Has anyone really been far even as decided to use even go want to do look more like?

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    BigBella's Avatar
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    Quote Originally Posted by Tony Paroubek View Post
    Other things to consider:
    It takes roughly 4 gallons of water to get one gallon of purified water. IE 3 gallons go down the drain while 1 is purified. If you pay alot for water a RO system may not save you all that much if you have access to cheap RO water from the supermarket or something. Don't forget to factor in the cost of replacing prefilters. Particularly the carbon block, which yyou should always get a quality one and replace it a couple times a year. If not you risk punching holes in the RO membrane from chlorines added by municipal water companies.

    Look for at least a 3 stage system. One particle prefilter, One carbon block prefilter and the RO membrane. You may find systems with post filters but I wouldn't spend extra for them.


    oh yeah.. you also want a system that has standard size filter housings so that you can shop around for filter replacements and not get stuck having to buy a certain filter. This would also allow you to replace your RO membrane at a later date should you need more output or to replace it when it water quality decreases over time.
    I have to agree with Tony's assessment of the sometimes dubious cost-benefit of RO systems. In CA, where we are experiencing a bit of a drought, the prospect of dumping three gallons to simply achieve one RO gallon is becoming more costly to the homeowner by the minute; also, depending upon how "hard" your water is, you can find yourself going through filters -- as I did -- at a rapid pace, and they are far from inexpensive.

    I have had two RO units over the years and perhaps will get another down the line, but I have found the cost -- gasoline included -- of filling a couple of five gallon bottles from a Glacier Water Machine outside of Safeway far more economical.

    There is some lifting of course . . .
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