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stanley
10/08/2008, 09:29 AM
I've got a slight problem and I was wondering if someone had an answer to my question. My 4 stage ro/di filter has no out put. The unit is less than 6 months old and when I turn it on, the waste water line is flowing like crazy but I am not getting any final output. It has been working fine since I bought it new and it just stopped one day this week. Any ideas??

schneijt
10/08/2008, 05:46 PM
Where did you get your unit? What brand is it? There should be a flow restrictor on your waste line that restricts the output of the waste line, thus producing purified water coming out of the membrane. Though your description is bare-bones and you have no pictures of the unit posted, it sounds like you may have a problem with your flow restrictor. There should be a 4:1 ratio, as in four parts of waste water for every one part purified RO water. I'd take a look at your flow restrictor and see if maybe that is the problem. There are several high-quality units out there...and several more low quality units. Depending on where you got your unit and who makes the unit, you may be dealing with a flawed system or a malfunctioning part or something like that. Or, alternately, you may have an outstanding company to turn to for help with your unit. It really depends on your unit and supplier.

-Joe

p.s. AZDesertRat is the RO/DI guru on here, so he'll probably see your thread and offer his two cents, which are worth a lot more than my two cents even in our terrible economy.

AZDesertRat
10/08/2008, 06:20 PM
Whats the tap water temperature and pressure? Whats the pressure at the membrane?
For a real quick test to see if the prefilter and carbon need replacing, remove both, screw the empty canisters back on and see if you get production now. If so the prefilter and carbn need replacing. They should be replaced at 6 month intervals anyway and you disinfect the system at the same time.
You don't happen to have a flush valve on it do you? Maybe its in the open or flush position?

saintperez
10/11/2008, 10:25 PM
AJ, maybe you can explain to me what the point of the waste water is? I mean, most filter systems have a single in and a single out, meaning there is no waste. Water just gets purified inline. Why do these RO/DI units have waste? And is the ratio of waste to ro water supposed to be higher than the RO water? I just plugged in a FilterGuys unit I bought used from someone that had it running for a year. I need to get new cartridges but basically wanted to know if the waster water ratio will be more equal to the RO output with new cartridges?

AZDesertRat
10/12/2008, 01:00 PM
The recommended 4:1 waste ratio is what keeps the membrane flushed and clean.
A RO membrane is a piece of extremely thin semipermeable plastic film sandwiched with what looks like very fine window screen and wrapped around a core. Pure water atoms pass through this film and the larger particles or contaminants stay on the surface to be carried away by this flush or waste stream.
This article sort of explains it:
http://www.dow.com/PublishedLiterature/dh_006c/0901b8038006cc4b.pdf?filepath=liquidseps/pdfs/noreg/609-00225.pdf&fromPage=GetDoc

Without the waste flow the membranes surface would soon plug or foul and the membrane would become useless. The ratio needs to stay at 4:1 or 4 gallons of waste for every 1 gallon of product or good water. Some will try and tell you you can get by with less but it will end up costing you in the long run with shortened membrane life. The other important factor is quality prefilters and carbon blocks, don't skimp on quality since those are what protects the membranes from the really big stuff and from chlorine. Get the smallest micron sizes you can and look for absolute rated prefilters over nominal rated filters, the diffrenece in quality is significant.

Some units have flush valves but I have yet to see an evidence from anywhere that proves they do anything other than lighten your wallet. Once dissolved solids begin to collect on the membrane no amount of flushing in the world will ever get rid of them. Stick with the 4:1 whenever the unit is in use and goodfilter replacements on a 6 month interval and you should get years of use out of a single membrane.