RO/DI unit broken! &%$#*!!

Do you ever flush your RO membrane???

 

That's odd. The 4 pre-membrane filters for the 5 stage Typhoon from airwaterice.com comes in a set for $39.99, that includes a new, refillable DI cartridge. The RO membrane from them can be had for about $50 or less if remember correctly.

I'm sure I'm preaching to the choir here, but you're spending way too much. Look into airwaterice.com. Don there is great. He responds to emails, and his cust. service has been nothing but stellar IME.

 

Most ebay quality RO and RO/DI systems come with cheap filters, some about as effective as a screen door.
When shopping for a reef quality RO/DI you need to look for several important things. First off, forget you ever heard the word "STAGES". It doesn't make a hill of beans, its a sales ploy the ebay vendors started to make their cheap units sound like the best thing since sliced bread. What is important is what filters are contained in those stages. Just because a unit has 5 stages or 7 stages doesn't mean its any better than one with 4 stages, in fact 4 stages is the magic, preffered number, 4 thats it no more.
You want a good quality prefilter, the lower the micron rating the better and an absolute rated prefilter is far better than a nominal rated filter. I suggest 1 micron or less, I run a 0.2 micron absolute rated prefilter personally. Next you want a single, yes only 1 carbon block. Not 2 or some granular carbon and a block but only one single low micron carbon block. You don't need a higher micron carbon in front of it because you have a high quality prefilter remember, now the carbon does not have to act as a secondary prefilter and can do the job it was designed for since it will not be plugged with particulates. A Matrikx+1 0.6 micron Chlorine Guzzler is best and works well even in chloramine situations contrary to what some believe.
The standard or the RO industry is the 75 GPD Dow Filmtec RO membrane and its what most legitimate vendors use. The GE 100 GPD is also a good membrane and is almost identical to the 75 GPD Dow in every way including real world GPD. Both produce 75 GPD at 50 psi, 90 GPD at 60 psi and 100 GPD at 65 psi, they just advertise them differently. DO NOT buy a Dow Filmtec 100 GPD at any cost, it is the worst possible choice and is not even a RO membrane at all but is in fact a Nano Filter approved for Pool and Spa Use by the ANSI/NSF. Its ony 90% efficient vs 96-98% efficient for the others.
DI filters should be vertical and in a standard 10" housing just like the prefilter and carbon. The cartridge should be refillable and plumbed so it has a bottom up flow pattern for best performance. Resins come in a multitude of qualities so stick with trusted vendors as resin has a shelf life even when kept sealed.

Inline TDS meter are not as accurate as handhelds since they are not truly temperature compensated. The temp probe resides outside the probe in air not water and the two are rarely the same which can lead to big discrepencies. They should be used as a guide and a good handheld should be used when you want accuracy. I use the HM Digital COM-100 myself but their TDS-3 and TDS-4 with the temp option are good too.

RO flush valves have no proven benefit other than lightening your wallet. Most who have them do not use them correctly anyway. For a membrane to last it needs to have a waste ratio of 4:1 constantly and the best way to achieve this is with a capillary tube type flow restrictor that you take 10 minutes trimming for your exact conditions and forget it. Most vendors use non adjustable fixed type restrictors and they are never right, everyones water pressure, TDS and temperature are different.

A few vendors I have not seen mentioned are Buckeye Field Supply which has a 75 GPD that fits the above perfectly including a inline pressure gauge, all the filters mentioned, a handheld TDS-3 meter, a RO bypass valve and only $169. Another is Spectrapure with their MaxCap which exceeds everything above and adds a second DI filter and 100% individually hand tested and guaranteed 98+% rejection membrane. Another is PurelyH2o with their Optima series. Yet another is Melevs Reef with his 100 GPD GE membrane system.

Lots of options and all have true reef quality systems.

And by the way, the TDS readings you are getting have no decimal places, they are whole numbers like 083 or 100 not .083 or 0.14 etc. No hobbyist grade TDS meter reads in fractions except the COM-100 and it only reads to tenths. The meters have a LCD screen with 3 or 4 digits but they are whole numbers not fractions.

 

Yeah what he said!!!!!

 

I second that. I get my 5 stages replaced for about $120, which includes 3 replacements of DI resin. My 100GPD membrane is $60, sediment and 3 carbons are $34 and DI resin is $18. I just changed out one of my drinking water carbon stage to a second DI stage, so it's even $9 less now.

 

DO NOT get a 100 GPD membrane if it is a Dow Filmtec! if its from Applied Membranes or GE Desal thats OK since they are basically a 75 GPD Dow Filmtec but the 100 GPD dow is not even a RO filter but is in fact a Nano filter which is only 90% effcient vs 96-98% for the others mentioned.

All you need is one good 1 micron or less prefilter, one good carbon block like the 0.6 micron Matrikx+1 chlorine guzzler, a Dow 75 GPD RO membrane and a single 10" cansiter style vertical refillable DI. If you want to invest any more add a second DI not a second carbon or anything else. Dual carbons go way back years ago when carbon was not as effective as it is today. Big improvements have been made over the years and all the best RO/DI vendors only use one even with chloramines where DI is as or more important than carbon.