How often do you replace RODI filter media?

Ecotech Marine
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When the unit flow becomes quite slow
 
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squampton said:
My tap is very consistent 10-13 TDS.

I have had this unit running 2 years almost, I do change the carbon filter twice a year, but the sediment filter, haven't changed it yet, no drop in pressure, and when I took it out and looked at it, looks mostly brand new still, so I don't see a need to change that one until there is a drop in pressure.

I don't use DI, I get 0 on 2 different TDS meters one inline and one handheld, and no negative effects on the tank, and a lot of local reefers don't use DI, and some just use straight tap with prime.
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That’s some good water! We’re area are you in ?

joqubr said:
in New Orleans 250-300 TDS going in 0-2 TDS coming out -5 stage system i only make about 50 gal a month, changed DI once in 12 months changed mostly because it was not packed tight the first time
Click to expand...

Those are some number these
 
Tidal Gardens
If you haven't checked out our Frequently Asked Questions section - have a look: FAQ's

Our very first FAQ addresses your question:

A good rule of thumb is to replace your sediment filter and carbon block after six months. A more precise way to maximize the usable 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 more of the prefilters (all the filters that touch the water before it reaches the RO membrane) is beginning to clog.

Also be cognizant of the chlorine capacity of the carbon block. A good 0.5 micron carbon block for example will remove much of the chlorine from 20,000 gallons of tap water presented at 1 gpm. Some original equipment suppliers commonly provide carbon cartridges rated at 2,000 to 6,000 gallons. Remember that all the water you process, both waste water and purified water, goes through the carbon block.

Regarding your RO membrane and DI resin, use your total dissolved solids (TDS) meter to measure, record, and track the TDS (expressed in parts per million [ppm]) in three places: 1) tap water, 2) after the RO but before the DI, and 3) after the DI.

The TDS in your tap water will likely range from about 50 ppm to upwards of 1000 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 do very little to remove dissolved solids. So with your tap water at 400 ppm, you can measure the water at the “in” port on your RO membrane housing and you'll see it is 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 96% (i.e., they reject 96% of the dissolved solids in the feed water). So the purified water coming from your 100 gpd membrane would be about 16 ppm (a 96% reduction). Filmtec 75 gpd (and below) membranes produce purified water (a.k.a. “permeate”) more slowly, but have a higher rejection rate (96 to 99%). The lifespan of an RO membrane is dependent 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 TDS in the water coming into 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 purified water more slowly as their function declines.

After the RO membrane, water will flow to your DI housing. DI resin in good condition will reduce the TDS in the RO water down to 0 or 1 ppm. When the DI output starts creeping up from 0 or 1 ppm, your resin needs to be replaced. Sometimes you'll hear people complain that their DI resin didn't last very long. Often the culprit is a malfunctioning RO membrane sending the DI resin high TDS water. This will exhaust the resin quicker than would otherwise have been the case. Sometimes the problem is poor quality resin – remember that all resins are not created equal.

Additionally, don’t forget to sanitize the entire system at least once per year, and wash and lube your housing o-rings with food-grade silicone grease every filter change.

Russ
 
I’m trying to figure out why I’m using so much di resin. I’m using well water with 98 TDS from the tap. After the RO it’s 2-3 TDS. 0 TDS after the DI but my resin only produces 90-100 gallons before the TDS goes to 1. Any suggestions?

Dave
 
Top Shelf Aquatics
View ReefStash's latest YouTube video!
9 ppm CO2 - just like having 9 extra ppm TDS in your RO water. - this would not cause what you're seeing in terms of fast DI resin exhaustion.
 
Yes but it start changing from the bottom up. Is the canister supposed to be completely full of water?
 
What I'm wondering is if your anion and cation DI beads separated - which typically appears like a color change starting at the top.

Its not critical for the entire housing to be full of water, but if you have an ASOV valve it will work better if you burp the air out of the housing.
 
Tidal Gardens
HM Digital DM1:Dual on the Rodi unit and I used a HM Digital hand held unit to verify.
 
BRS
AI Hydra

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