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Thread: need help getting an RO unit

  1. #25
    Av8tor1's Avatar
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    Fry,

    there is really not much diff in price between a 50gpd system and a 10o gpd, unless you need more then 125 the price is pretty much the same.

    the difference in cost comes from various combination of components... if you are use it for reef you dont need a captive air tank, if you use it for Cp's you normally would want one. There is also a diff in quality of prefilters, you can get a cheap 10 or 20 micron and save money there only to have to replace your expensive membrane prematurely

    UV's are cool but overkill for CP's, I wouldnt use one of them unless I had a reef system with ubber high dollar corals and fish, plus if you check into those you will see the bulbs must be replaced very regularly

    these are somehtin you buy once and keep it for many years, you can buy a system that will need 30$ worth of filters and 50$ worth of membranes pretty frequently, or you can spend a little more upfront and get much longer life out of your prefilters and years out of your membrane

    and then there is the waste water issue...

    my recommendation stands, figure on 150-200 for a good system that will be efficent and last for years with low maintenance

    etc etc etc,

    but, sometimes budgets wont allow it I know... in those cases you gotta do what you gotta do


    HTH's
    Av

  2. #26
    --Freedom Czar-- Fryster's Avatar
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    Yeah, I figured on a $150-$200 price range; as long as it's a good system that will last me a number of years with moderate use.

    So, the pre-filters are an important part of the system that will help add longevity to the more expensive membranes, is that correct?

    And pre-filters are the first, second and third stages, correct?


    (ugghhh....so much to learn.......so little time..........)
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  3. #27
    Av8tor1's Avatar
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    yes... and good quality prefilters definitely cost more, so you want all the life you can get out of them... this is where the permeate pump comes into play

    as the captive air tank fills, pressure downstream of the membrane increases... this increase in downstream pressure means that the pressure differential across the membrane (diff in upstream compared to downstream) decreases. This decrease in differential results in a proptional increase in brine rate. This then means the prefilters are having to do a lot of work they wouldnt be doing with a permeate pump (which isolate the captive air tank pressure from the membrane outlet)

    with the permeate pump, brine rate decreases, prefilter life increases, water usage decreases, recycle times improve, rejection ratio improves, membrane life etc

    and be sure to get a TDS meter and PSI gauge, IMHO you will need them in the long run

    Av

  4. #28
    Av8tor1's Avatar
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    permeate pump link

    (not meant to be a vendor recommendation just a FYI)

    Av

  5. #29
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    I got the AquaSafe one on ebay a few years ago, still works great. Had to change out the prefilters once, but they're cheap if you buy 3 sets at once.
    larry
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  6. #30
    Let's positive thinking! seedjar's Avatar
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    I've actually heard that most pre-filters don't do a whole lot to extend membrane life... At least, that's the impression I got from actual users when I was shopping around for my RO unit. It's sad to hear that Aqua-Safe's quality is going down - I got an Aqua-Safe rig with a four-gallon tank for less than $150, including shipping, and it works great. That was two years ago, though.
    Interesting info on the permeate pump, Av... I might have to go pick one of those up this summer. Do you think that adding one of those could get my holding tank to actually retain its entire four gallon capacity? Right now, my next filter-related purchase is probably going to be a pump for the input, as I'm far from the local station and my pressure is super low. I want to have more water on hold and figured that buying another tank and further decreasing the pressure differential would probably be a waste of my money... a line pressurizer seemed like the best option. You wouldn't happen to know how these types of pumps typically stack up, do you?
    ~Joe

    PS - Er, I know the prefilters serve some purpose... Large sediments can harm the membrane. I think the particulate filter is the key part, but you don't actually need the activated carbon and some of the other stages that are included... Come to think of it, ignore me and do your own research...
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  7. #31
    --Freedom Czar-- Fryster's Avatar
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    Hmmm......

    That certainly is an informative site. Is RO technology closer to brain surgery or rocket science?? I just may have to go back to school to learn all this stuff. Setting up a home network was less confusing..... And that is why it's good to know people on here to ask questions, exchange information and such.

    So it sounds as if a permeate pump extends the life and efficiency of the RO unit as a whole; is this correct? And a pump would require an electrical cord coming out from under my kitchen sink, yes? I'm sure that it doesn't take AAA batteries.

    I have a TDS meter. That's how I know that my water is so crappy; 325ppm right outta the faucet. I've grown accustomed to the flavor of nickle.............


    ***Seeing pictures of other people's RO set-ups would be kinda helpful.
    Only a moral and virtuous people are capable of freedom; the more corrupt and vicious a people becomes, the more it has need of masters. -- Benjamin Franklin

  8. #32
    Av8tor1's Avatar
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    Quote Originally Posted by seedjar View Post
    I've actually heard that most pre-filters don't do a whole lot to extend membrane life... At least, that's the impression I got from actual users when I was shopping around for my RO unit. It's sad to hear that Aqua-Safe's quality is going down - I got an Aqua-Safe rig with a four-gallon tank for less than $150, including shipping, and it works great. That was two years ago, though.
    Interesting info on the permeate pump, Av... I might have to go pick one of those up this summer. Do you think that adding one of those could get my holding tank to actually retain its entire four gallon capacity? Right now, my next filter-related purchase is probably going to be a pump for the input, as I'm far from the local station and my pressure is super low. I want to have more water on hold and figured that buying another tank and further decreasing the pressure differential would probably be a waste of my money... a line pressurizer seemed like the best option. You wouldn't happen to know how these types of pumps typically stack up, do you?
    ~Joe

    PS - Er, I know the prefilters serve some purpose... Large sediments can harm the membrane. I think the particulate filter is the key part, but you don't actually need the activated carbon and some of the other stages that are included... Come to think of it, ignore me and do your own research...
    the holding tank capacity will not change as long as you still use the 60% auto shut off valve, it stops flow once pressure downstream of the membrane reaches 60% of pressure upstream of the membrane. This amount of diff is required so the pressure diff stays at a level high enough to work, otherwist the brine rate would keep increasing and the unit would never shut off.

    with the permeate pump you can run a 90% ASO vavle due to the isolation of the tank from the membrane output, this increase in outlet pressure will increase the tanks usable volume

    but you must understand how the captive air tank works, it is basically a hydropneumatic accumulator.. i know big words... but it has bladder in it that is surrounded by "air" under a low pressure... now fluid flows into the tank compressing this air untill the air pressure matches the fluid pressure... so the amount that the tank can hold depends on the relationship of the air precharge pressure as compared to the max membrane outlet pressure

    in other words if you water pressure is low, the two will balance before the bladder has expanded to fill the void in the tank, but if the pressure is high in relation to the prechare pressure the bladder will fill untill the void inside the tank is more full, holding more if not all of the full volume possible (rated volume)

    Personally, i am a big fan of good prefilters... I have seen the life of my membrane and DI beads increase, remember the output TDS quality of the membrane is directly proportional to the input TDS... so if my membrane has a 95% rejection ratio and my input TDS is 1000 at the membrane the output will be 50ppm, whereas if the input to the membrane is 100 TDS the same membrane would have an output of 5 TDS

    if your pressure is low then nothing will work like it should and it will be very inefficent

    chlorine will destroy the TFC membrane material, so activated carbon is very important... now there is a membrane type that is chlorine tolerant... hmmm seems like it is CFC but I dont remember, but these are not very common in our hobby, the post membrane carbon filter is there mainly to remove any VOC's and bad taste that may come from the bladder itself.. so while not technically required, it does serve a purpose as well

    mine is an old aqua safe as well, and it is a shame, they no longer use the same high quality DI housing or flush valve

    but they have to stay competitive with the others on ebay, so I cant blame them I guess

    Joe, if you want good stuff... go to spectrapure.com, they are the porche of RO... see what brands they have and look for less expensive source if they are too high

    fry, the permeate pump requires no electricity, it is powered by the brine outlet flow (very slick engineering BTW)

    Av

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