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RODI Replacement Cannisters

Jeff Rehling

Jeff Rehling

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Question...my first stage of my RODI unit is very discolored and that tends to indicate it's time to replace it. My pressure has declined only by 1-2 PSI. Do i only need to replace the first canister or all three?
 
How many stages you have?
What's your first stage?
I change the first 3 stages once it reads anything not zero.

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Oh got it.
Well if it's me I would change all stages cause once you started seeing tds it might mean the di reain is depleted as well.
Otherwise start changing the first stages and keep do resin bit longer and see. But honestly I think it's not big diffrent cost wise so I would change all and start fresh.

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First three stages are typical going to be a mixture of carbon and sediment filters, and often you'll have 2 of one kind and 1 of the other, a very common setup is a sediment filter then 2 carbon blocks, 2 just as a back up to make sure all chloramines are pulled out. The problem is carbon really doesn't have any color indicators to let you know that it's ready to change, any color that's on them is due to sediment that gets through that filter and really isn't what those filters are removing. Having some sort of flow meter that records how much water goes through them is the most ideal situation, however an easy second step is to have a tee with a valve right after the first 3 filters and periodically test the output with chlorine test strips, and the easiest way is to see how fast your DI resin gets used up, if you notice a very rapid change then it's pulling out more stuff than it was likely chloramines.
 
Oooh - didn't know I could use chlorine test strips at that point to test for chloramine - will get some strips!
Jumping in with a related question - if you test your TDS at that T after the sediment and 2 carbons, could it be higher than the input TDS from the tap? Why would that be?
 
MolaMola said:
Oooh - didn't know I could use chlorine test strips at that point to test for chloramine - will get some strips!
Jumping in with a related question - if you test your TDS at that T after the sediment and 2 carbons, could it be higher than the input TDS from the tap? Why would that be?
Click to expand...
My chemistry is almost non-existent, but I believe you want "total chlorine" as opposed to "free chlorine" which I'm not sure detects chloramines.
 
sfsuphysics said:
My chemistry is almost non-existent, but I believe you want "total chlorine" as opposed to "free chlorine" which I'm not sure detects chloramines.
Click to expand...

Correct. Free chlorine just tests for chlorine that is not bound to anything. You will need a test stripe that tests for total chlorine to detect chloramines.
 
My water source have chloramine which is the worst. That's why I use 7 stages rodi. It's an overkill but it last me more compared to when I ran 5 and 6 stages...
Also I try to keep zero tds water and change filters once last stage start showing 1 tds..

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@Jeff Rehling visual discoloration does not indicate time to change. It will look dirty quickly but work well for some time still. 1-2 psi drop isn’t much.
Your chloramine block probably needs to be changed every 1500 gal of total water through out depending on what one you use. That counts waste and product. Only way to know for sure is to monitor the galllns you put through it.
Text r call me if you have questions. Don’t have time or feel like typing a long response right now.
 
MolaMola said:
Oooh - didn't know I could use chlorine test strips at that point to test for chloramine - will get some strips!
Jumping in with a related question - if you test your TDS at that T after the sediment and 2 carbons, could it be higher than the input TDS from the tap? Why would that be?
Click to expand...
I test Tds main input, at output of of carbon blocks(input of ro membrane) at input of di and at output of di.
My main input is aweful around 135,
My ro membrane output.is around 12 and my di output is 0

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Coral reefer said:
@Jeff Rehling visual discoloration does not indicate time to change. It will look dirty quickly but work well for some time still. 1-2 psi drop isn’t much.
Text r call me if you have questions. Don’t have time or feel like typing a long response right now.
Click to expand...
The only visual discoloration that indicate time to change is the color changing di resin. If you use color changing di resin, color is good indication to depleted.
That being said, it's all about tds for me, tds above zero, time to change

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