DI Resin Capacity (Poll)

How many gallons of DI water do you get before you replace your DI resin? Some systems have multiple canisters, large canisters, inline canisters, etc., so please approximate in terms of gallons per each standard vertical 10" canister.


I'm just curious how many gallons of 0 TDS people typically get before their DI resin is exhausted. I'm getting ~100 gallons tops, which I suspect is very low compared to most. Please mention any information that you think is relevant.


My current setup:

• Supply: Well Water
• Conditioning: Kinetico water softener & Sulfur Guard
• TDS Before RO: 250 ppm, March 2014 (has been as high as 450 over the last 4 years)
• RO system: BRS 5 stage drinking water (with dual DI canisters), using both booster pump and permeate pump, flushed regularly.
• TDS after RO, before DI: 4-5 ppm (~98% rejection)
• TDS before DI (different meter): 4-5 ppm
• DI setup: BRS dual 10" canister, using BRS color changing resin. I rotate & change one canister when output TDS goes from 0 to 3-4 ppm. I always remove the first DI canister, rotate the 2nd canister to the first position, and install a new canister in the 2nd position.
• TDS after DI: 0 ppm for ~80-90 gallons, then creeps up to 3-4 ppm by ~100 gallons.

Why is my DI exhausting so soon? I would expect that it should be able to produce significantly more DI water before replacing resin. I think I know why--more to come later after I confirm a few things. But for now, am curious how my DI usage stacks up to everyone else.

 

I can't edit my original post any longer. I didn't realize a long poll question wouldn't text wrap. I would like to add a few carriage returns / line breaks to the question so the page is easier to read. Can a moderator do this for me? Thanks!

Very true...I suspect. This concept is what really got me thinking. I replaced my Kinetico RO system with the BRS system because 1) my Kinetico system stopped working and it was going to cost an arm and a leg to repair, and 2) it had ~90% rejection rate. At the time my source water TDS was 430 ppm and my RO was 40-45 ppm. I was only getting ~70 gallons DI water before the canister was exhausted. I figured it would be really easy to justify the cost of a new standard, non-proprietary, RO system with a membrane rated for 98% rejection rate--I went with BRS. My calculation was that if I could improve the TDS of my RO water by a factor of 10, I would see a 10 fold increase in the life of my DI resin.


This was not my experience, even though my TDS readings confirmed my original theory.


What was I missing? Hints: well water, pH of my RO water is 5.6 (calibrated pH probe), alkalinity of my RO water is between .3 and .5 dKH (Salifert test kit).

 

I am on a well, and its not uncommon for well water to have high levels of dissolved carbon dioxide. CO2 goes right through an RO membrane and TDS measurements don't pick it up. CO2 can exhaust DI resin very rapidly. I spent some time googling and I found that there are a lot of reefers who burn through DI resin because of CO2 in their water. I ran across this calculator (http://www.hamzasreef.com/Contents/...letion.php) and from it, I would estimate that CO2 is depleting 80-90% of my DI resin!

 

I really only found a couple ways to get rid of the CO2. The most common to degas RO water before pumping it through the DI stage as explained here: http://spectrapure.com/frequently-a...ns#calcc02


Degassing takes time, bubbling tower, open storage tank, etc. Then you need another pump or use gravity to push water through the DI stage. The only other solution that I ran across was sodium hydroxide injection, which is complicated, risky, and expensive. I would prefer not to have to set up a degassing station and the chemical injection is just not a practical option.

 

I'm going to experiment with something different. I discussed my idea with Jeremy at SpectraPure and he made me a special canister to put in place of one of my carbon blocks in my RO unit. I expect the canister will contain blend of a media that will safely neutralize most (hopefully all) of the CO2. This result may be increased hardness but the RO membrane will have no trouble rejecting the extra minerals.

UPS tracking says my SpectraPure package is out for delivery today, so I am anxious to open it up. I also ordered a CO2 test kit and some MaxCap/SilicaBuster resin. I'm hoping the CO2 test kit will be easy to use and support the pH/Alk/CO2 calculator. I will be using BRS DI resin at first to see if there is an improvement, then I will switch over to MaxCap/SilicaBuster for a test drive.

 

Last Sunday I had a couple hours to experiment with the stuff I got fromSpectraPure. I started by using the CO2 test kit to check my tap water and RO water (with ~1 year old filters) to establish a baseline CO2 level. I should comment that I thought the CO2 test kit was relatively easy to use.

• I checked my (softened) tap water twice and CO2 was 35 ppm the first time and 34 ppm the second time.
• I checked my RO (with old filters) twice and CO2 was 44 ppm the first time and 42 ppm the second time.
• The CO2 was in the ball park that I expected from when I used an online calculator to come up with ~30 ppm.

Next I was anxious to install the special formula remineralization canister from SpectraPure. I replaced the first 3 stages in my RODI system. The old configuration was 1) sediment filter 2) 5 micron carbon block 3) 0.6 micron carbon block. The new configuration has the remineralization (Spectrapure FA-REMIN-101) in the 2nd stage and there will only be one carbon block since I do not have chlorine/chloramine to remove.


I needed to flush the fines out of the system from the REMIN cartridge, so I waited to install the cartridge block and flushed my RO membran until the water coming out of the REMIN cartridge was clear. One attached picture shows how cloudy the water was when I started to flush the fines out. When the water ran clear, I rinsed out the 3rd stage housing and installed the carbon block. I let the RO system run for a while before I tested the CO2 level.

• I checked the RO after the REMIN cartrige was installed and CO2 was 23 ppm.

The special REMIN cartridge didn't eliminate the CO2, but it cut it roughly by a third to a half. Not the results I was hoping for, but it is a step in the right direction. I installed a new DI canister and I expect it to have much improved life.

 

I've produced over 110 gallons of DI and I still have 0 TDS, so I can already report an improvement.

 

TDS went from 0 to 1 after 145 gallons DI. I will wait to change the DI resin until TDS goes up some more and to see what happens.

This is better than before when TDS would start to creep up around 80-90 gallons. So far, I think the special demineralization cartridge is helping improve my DI life by removing some of the CO2 that is present in my well water.