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Old 08-31-2007, 10:02 AM   #1 (permalink)
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Default How often should you change your RO/DI filter Media?

How often is the normal amount of time to wait before changing the filter media in your RO/Di unit?
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Old 08-31-2007, 10:17 AM   #2 (permalink)
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I bought my RO/DI around this time last year, I am getting ready to make my first change...I keep a log of how often I am running my RO/Di..I wait until my 75 gallon is almost empty then I will run it for 3 days to fill up the container and mark of that I used 75 gallons of water...According to the manufacturers are supposed to change the media every 800-1000 Gallons...

I would check with the manufacturer of your RO/DI and see what the specifications suggest...bring a sample of your water once in a while to your LFS and ask them to check the levels in your water...this is a good way to test the water quality and see when it is time to change your filters...

Atleast this is a really effectice way for me...I do a clean test with a new filter and then around 500 gallons later test again, and then right at 800 gallons I test again and this gives me an acurate idea of how the quality is affected over time...

Hope this helps...
210g Display, 90g Frag tank and a 100g Stock Tank Sump.

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Old 08-31-2007, 10:33 AM   #3 (permalink)
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if you buy a tds meter for the export ryan all you would have to do is watch the output and that should tell you exactly
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Old 08-31-2007, 11:11 AM   #4 (permalink)
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Originally Posted by broncsyanks View Post
if you buy a tds meter for the export ryan all you would have to do is watch the output and that should tell you exactly
Mat whats up buddy? You RO/DI setup is rediculous... You should post a pic of your system.. like 8 stages lol
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Old 08-31-2007, 12:21 PM   #5 (permalink)
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I've heard that phosphates will not show up on a TDS meter. If that is true using a tds meter as a gauge for when you DI resin has been exhausted is no good. I use the color changing stuff from buckeyefiledsupply. As soon as it starts to change color I change it. I also change out my sediment filters just about monthly.
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Old 09-06-2007, 11:16 PM   #6 (permalink)
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If your unit uses clear housings then you can also gauge by eye and, by out put-
which starts to diminish when the filters are spent.
To test accurately for phosphates you need a Hanna low range phosphate meter.
These are expensive but the only way to get true readings......HARK....
they also happen to be on sale right now for the lowest price I've ever seen-
I got mine , did you get yours?!
over 30 yrs marine experience...
Been There Done That!
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Old 11-04-2007, 03:21 AM   #7 (permalink)
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A good rule of thumb is to replace your sediment filter and carbon block after six months. A more precise way to maximize the useable life of these two filters is to use a pressure gauge to identify when pressure reaching the membrane starts to decline. This is your indication one or both of the filters is beginning to clog.

Also be cognizant of the chlorine capacity of the carbon block. The Matrikx+1 (“Chlorine Guzzler”) for example will remove 99% of chlorine from 20,000 gallons of tap water presented at 1 gpm. Original equipment suppliers commonly provide carbon cartridges rated at 2,000 to 6,000 gallons.

Regarding your RO membrane and DI resin, use your TDS meter to measure, record, and track the TDS (expressed in parts per million) in three places:
1. Tap water
2. After the RO but before the DI
3. After the DI.

The TDS in your tap water will likely range from about 50 ppm to upwards of 1000 parts per million (ppm). Common readings are 100 to 400 ppm. So for sake of discussion, let's say your tap water reads 400 ppm. That means that for every million parts of water, you have 400 parts of dissolved solids. How do we go about getting that TDS reading down to somewhere near zero?

If you do some experimenting with your TDS meter, you'll note that your sediment filter and carbon block filter (collectively called prefilters) do very little to remove dissolved solids. So with your tap water at 400 ppm, you can measure the water at the “inââ €šÂ¬Ã‚ port on your RO housing and you'll see its still approximately 400 ppm.

The RO membrane is really the workhorse of the system. It removes most of the TDS, some membranes to a greater extent than others. For instance, 100 gpd Filmtec membranes have a rejection rate of 90% (i.e., they reject 90% of the dissolved solids in feed water). So the purified water coming from your 100 gpd membrane would be about 40 ppm (a 90% reduction). Filmtec 75 gpd (and below) membranes produce less purified water (aka “permeateà€), but have a higher rejection rate (96 to 98%). The life span of a RO membrane is dependant upon how much water you run through it, and how dirty the water is. Membranes can function well for a year, two years, or more. To test the membrane, measure the total dissolved solids (TDS) in the water coming in to the membrane, and in the purified water (permeate) produced by the membrane. Compare that to the membrane’s advertised rejection rate, and to the same reading you recorded when the membrane was new. Membranes also commonly produce less water as their function declines.

After the RO membrane, water will flow to your DI housing. DI resin in good condition will reduce the 40 ppm water down to 0 or 1 ppm. When the DI output starts creeping up from 0 or 1 ppm to 3 ppm, 5 ppm, and higher, you know that your resin needs to be replaced. Sometimes people complain that their DI resin didn't last very long. Often the culprit is a malfunctioning RO membrane sending the DI resin “dirtyâà ¢â€šÂ¬Ã‚ water. This will exhaust the resin quicker then would otherwise have been the case. Sometimes the problem is poor quality resin – remember that all resins are not created equal!

Russ @ BFS
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