Info on RODI System

[mike31154]

I started using my RODI system in mid April 2009 & have kept track of water production/throughput on an Excel spreadsheet since that time. It's a 5 stage unit currently running with two poly pre filters (5 micron & 1 micron), a 'chlorine guzzler' carbon stage, 75 gpd RO membrane & DI stage. Always been skeptical of the 6 month or any time based filter change regimen suggested by many vendors & even some manufacturers. To me, logic dictates that it's more efficient & economical to monitor your water throughput & check parameters periodically to determine if a filter needs service or replacement, even if it's a cheapo 5 micron poly pre filter.

So here's some data. As of today & since 15 April 2009 I've produced 424 US gallons of RO water & 1823 US gallons of RODI water (total production 2247 US gals.). Now if I include all the waste water made during production @ 1 to 4 good/waste ratio, that means 8990 US gallons have passed through the filtration process. Using a 1 to 3 ratio it's 6742 US gallons. Numbers, numbers....

An important job of the carbon pre filter is to protect the RO membrane from chlorine which will eventually destroy it. This makes the carbon stage a component to keep a special eye on since the RO membrane is typically one of the more costly items to replace. The 0.5 micron MAXCL-975 carbon stage in my system is rated to remove chlorine for up to 20,000 gallons of water at 1 GPM. If I were to change it out at a 6 month interval rather than keeping track of water throughput, I reckon I'd be wasting some resources and money. Then again, manufacturer's ratings are subject to varied input parameters, therefore not absolute.

I've been meaning to test & ensure that no chlorine is getting to my RO membrane for a some time now, so the other day I installed a JG tee fitting & shutoff valve between the prefilters & RO membrane. This allows me to draw water from there & test for the presence of chlorine.... i.e. is my carbon block still doing its thing after more than 2 years & close to 9,000 US gals (estimated) throughput? Almost halfway to the 20,000 gal. manufacturer's rating. A swimming pool water test kit with strips that include a chlorine tab is what I decided to use for the check. The results are in the following photos. Looks like I'm still good to go.

The strip on the left is water drawn after the pre filters, the strip on the right is tap water. One of the photos is with flash, the other with no flash. In real life, the filtered strip really looked like 0 chlorine, by the photos you might be inclined to think perhaps 0.5 ppm chlorine. In any case, my point in this thread is to provide info for anyone interested in saving a buck or two & some resources rather than changing filters based on a given time period regardless of how much water is going through their RODI unit. Had I kept to the 6 month rule I'd likely be on my 4th carbon block by now. As it stands, I'm still on the first & it appears to be going strong.

[delo978]

wow thanks for the info.....I'm about to go RODI myself and was curious about the info you provided. Your dedication is appreciated.

Cheers

[mike31154]

He, he, I was starting to wonder if anyone took note of this info & found it of value. When it comes to saving money (resources too I guess), I'm pretty dedicated for sure.