Aquatic Life Twist in 100gpd RODI. It's a few years old. Has always read 0 TDS until recently it's reading 2-3. Water pressure is good. I changed all filters and RO membrane, swapped leads on my TDS meter, and no change. Another thing is that its not depleting the DI resin any more. The big difference of when it started was that I moved my tank upstairs, and kept the RODI downstairs. But it didn't seem to start until about 10 months in. Basically my filter is mounted on the wall downstairs, the waste water drains below the filter, and the RO water is pumped either A) upstairs to my ATO reservoir daily, (there is a check valve to keep it from draining back into the RODI) or B) to my mixing bucket downstairs next to the filter. Is there a problem with having the filter below the water outlet? Any ideas why my DI resin seems to be getting bypassed? @AquaticLifeProducts
DI Resin not depleting, high TDS
- Thread starter ianryd
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Duncan62
Valuable Member
Mabe a faulty di cartridge. 2 is still pretty good. Does the resin turn dark blue as it fills? Mine has depleted the first couple inches then began to bypass some. I added another di in line as a just in case thing.
I think I see what you are talking about, it's the cylinder coming off the RO membrane, feeding the red line right? Mine doesn't have a switchable valve though. It just has a sticker that says 800 with an arrow. Maybe it's clogged?
Duncan62
Valuable Member
That's a flow regulator. Controls flow thru the membrane. You should disconnect and flush occasionally. It tells how in instructions. You membrane will last longer.
Duncan62
Valuable Member
The clear plastic ones perform better. Those opaque ones are labeled the same but I don't think their as good.
I would be difficult to bypass the DI as it trickles from the top down and through a center pipe out the top.
When the new membrane was installed did you happen to flush the membrane for 30 minutes prior to adding the DI? The high TDS out of a new membrane can use the DI up quickly and the DI has a hard time removing the 300 ppm TDS from the water in such a short contact time. Lower TDS is no problem but if too high it will be difficult to remove.
If you install the flush cap on the DI now can you let us know the TDS of the RO filtered water compared to the supply water TDS? Looking to see the % of rejection.
Duncan62
Valuable Member
On my present unit I'm running 2 DI cartridges in line and the depletion level looks the same in both. Normal?
The DI resin in the first cartridge would be removing the incoming TDS first and the resin should deplete into the 2nd cartridge. You can verify with measuring the TDS with the flush cap on the second DI position to see the TDS output of the 1st DI compared the final output TDS.
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