Again, ignore the word "Stage", it means nothing. Pay attention to the filters that are contained in the stages not the number or amount of them. For a reef quality RO/DI you need 4 stages, thats it no more no less unless you want dual DI or have horrible sediment or particulate problems that may require a seperate filter.
The word stages became popular wit hthe ebay vendors who try to pass off low quality drinking water systems as reef quality systems. The use magic words like 6 Stages or 7 Stages and try to make you think you are getting the best thing since sliced bread when in fact you are getting a low quality drinking water system is all. Just because they add a post RO/DI granular carbon filter you will throw away since it actually adds TDS or a second granular carbon filter after the prefilter that only lasts 300 total gallons, yes 300 total so thats 60 RO/DI gallons and 240 waste gallons! Or two little horizontal hollow tubes with some outdated resin bobbing around and short circuits or channels so is ineffective at treatment.
You want a single prefilter in as low a micron range as possible so it does its job of protecting the expensive carbon block. Always get a prefilter the same micron range as the carbon block or smaller so it does not allow particulates and colloidal materials to plug or foul the billions of tiny pores in the carbon block. An absolute rated prefilter is far superior to a nominal rated prefilter, huge difference in quality and performance.
Next you want a single carbon block in the 0.5 or 0.6 micron range not two carbons. Two gives you greater pressure drop which slows production and lowers final quality. Even if you have chloramines stick with one 20,000 gallons chlorine guzzler, most utilities only feed 1 to 2 mg/L chloramines so a single carbon is more than sufficient in a 100GPD or less system. Actually DI is more important than carbon when itcomes to chloramines since the carbon takes care or only the chlorine portion, its the DI that polishes off the ammonia since RO only is only partially effective at all forms of amonia.
Next you want a 96-98% or higher rejection rate RO membrane since they are the workhorse. Remember this, for every 2% you increase the RO membrane efficiency you DOUBLE the life of your DI resin. This is why Spectrapure tests and treats their membranes for best performance, no one else offers this service or guarantee.
Lastly you want a full size 20 oz vertical DI with a bottom up flow pattern. If you want to improve upon anything add a second DI as with the MaxCap, this is where you get bang for the buck not carbons or prefilters.
You cannot get the same quality on ebay guaranteed. Yes some of the larger vendors like PurelyH2O sell on ebay as H2O Science but for $139 you get a basic system without a TDS meter or pressure gauge, and with large micron filters and little else. You will not get a tested membrane, specially blended DI resin, a capillary tube flow restrictor, etc.
Stages are not all equal so look at quality not quantity.
All public or community water systems must provide each user what the EPA calls a Consumer Confidence Report annually. The problem is its already a year old so again was a snapshot in time when it was sampled and it only has to contain those things that were tested in that calendar year. not all things get tested every year, many are on 3 year cycles so it may not contain everything. Its best to find a buddy at the utility who has an interest in the hobby such as myself. I used to get calls all the time asking about both freshwater and saltwater fish and coral keeping and I even kept a 37 gallon ref system in my office on display and had a freshwater system in the lab.
The Spectrapure system comes with a 98+% batch tested and treated high efficiency membrane, SilicaBuster DI resin, capillary tube flow restrictor, dual inline TDS meter, inline pressure gauge, hose bib adapter, 0.5 micron absolute rated prefilter, 0.5 micron 20,000 gallon chlorine guzzler carbon block and more. You can find the owners manual here:
http://www.spectrapure.com/manuals/PRINTER_FRIENDLY/CSPDI_MANUAL.pdf
Spectrapure is also a Sponsor of this site and has a Sponsors Forum with lots of great information for all. Check them out.
