Confused about RODI Chlorine testing

FishyFishFish

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I was going to use a chlorine test to determine when to replace my carbon block in my RODI unit, rather than changing it at a time interval. I have just tested the output from the carbon block for the first time, using the LaMotte Insta-Test test strips, and this test showed zero free chlorine but potentially up to 5 ppm of total chlorine.

I then tested the output water and the waste water and it shows zero of both.

I was under the impression that it was the carbon block that removed the chlorine. Do I need to replace the carbon block (which isn't very old) or is it ok to carry on using it if the water output is chlorine free?
 
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Biglew11

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The di resin will remove chlorine. If you have chlorine between the carbon block and the ro stage, the chlorine will break down the ro membrane.

You should definitely replace the carbon block.
 
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FishyFishFish

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I have done a bit more research and I believe that the problem is chloramines. I have seen a BRS video that suggests that 'normal' carbon blocks get depleted extremely quickly with regard to their ability to reject chloramines. My system is only a little RO Buddie and, whilst I do have a spare carbon filter, I am concerned that the new one might only last a few days if I replace it.

The questions I have now then are:

Will the carbon block still filter other impurities or will it have been destroyed by the chloramines?

How quickly will chloramines damage the RO membrane? It might be cheaper to wear that out rather than repeatedly change the carbon filter!
 

Biglew11

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Not sure how soon the chlorine will destroy an ro membrane. But they typically last around 3-5 years on a properly running system

is it possible to bypass the carbon stage and add a separate canister for a different carbon block.

use the 10 inch canister with 1/4 fittings
https://www.bulkreefsupply.com/reverse-osmosis-canisters.html

And a 10 carbon block
https://www.bulkreefsupply.com/pentek-chlorplus-carbon-block-chloramines-removal.html should probably get around 6 months or more depending on how much water you make, and chlorine chloramine in the source water.

Carbon block Should definitely last alot more than a few days. Are you positive you tested between ro and carbon, and not the incoming water before any filtering?
 
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DaddyFish

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Dwell time is paramount to the efficiency of a carbon block filter. Most 10" carbon block filters carry a rating of 1 gpm maximum flow, which is way above the flow of your RO unit.

My water system is a community well that uses chloramines. I suggest you start with additional carbon block filters ahead of the RO membrane if you're looking to make changes. I've found a 10-micron sediment, followed by two carbon block filters, followed by a 1-micron sediment to be extremely effective in keeping the RO membrane clear of incoming nasties.

With that filter arrangement I change carbon blocks every six months out of precaution, not necessity.
 
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FishyFishFish

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I’m positive that I tested after the carbon block; I tested at the T input to the RO membrane.

The BRS video showed that chloramines will very quickly break through the carbon filter. On the ‘standard’ carbon blocks they were showing significant breakthrough after a number of hours (not days). My RO Buddie carbon filter is smaller than a standard filter.

I could add extra parts but I’m trying to ascertain if I need to, if my output water tests ok.
 

Biglew11

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the carbon blocks are an expendable resource, you already have too change it out no matter what. after 6 months I still get no chlorine reading through my carbon blocks. why waste ro membranes if you don't have too? a good Dowfilmtec ro mebrane can last over 5 years $34 $45
edit. I should also note that I make 45 gallons of rodi a week.
https://www.bulkreefsupply.com/bulk...smosis-filters/reverse-osmosis-membranes.html
bottom line is the ro membrane is the most important part of the rodi unit. you want to make sure that you do everything to make sure its operating at it's max potential. this means changing carbon blocks when you have chlorine going into the ro stage. the ro membrane filters out the very fine particles. if it's destroyed by chlorine, chloramines, it will not filter these out, then they will go to the di resin which only remove ionized atoms.

specs for a 75gpd Dowfilmtec
https://s3.amazonaws.com/brsinstructions/brsRODI/BW60-1812-75membrane75gpd.pdf

taken from here
question.jpg


Can Thin Film RO membranes tolerate chlorine?

answer.jpg


Chlorine will oxidize the surface of thin film composite polyamide membranes, causing the membrane to lose its ability to repel or reject salts.

Thin film membranes can tolerate up to 1000 ppm-hours of chlorine. Traces of metals will accelerate oxidation. Therefore chlorine should be removed from the RO feed water.

two recommended carbon block that you already have to change for reasons other than just chlorines and chlorimines

  1. Filter Chlorplus


    Rating:
    91%
    Miscellaneous
    PENTEK CHLORPLUS CARBON BLOCK
    Starting at: $23.99

    Choose Options

  2. ChloraGuard 1 micron Carbon Block

    Rating:
    100%
    Matrikx
    CHLORAGUARD CARBON BLOCK - 1 MICRON - MATRIKX
    Starting at: $19.99

    Choose Options

    another site to check out the effects of chlorine on the membrane.
    https://www.waterworld.com/home/article/16199150/avoiding-testing-errors-protecting-ro-membranes-from-chlorine-damage#:~:text=Chlorine Damage,-To prevent oxidation&text=For Dow FilmtecTM RO membranes,be taken to20it prevent%.
 
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Randy Holmes-Farley

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I’m positive that I tested after the carbon block; I tested at the T input to the RO membrane.

The BRS video showed that chloramines will very quickly break through the carbon filter. On the ‘standard’ carbon blocks they were showing significant breakthrough after a number of hours (not days). My RO Buddie carbon filter is smaller than a standard filter.

I could add extra parts but I’m trying to ascertain if I need to, if my output water tests ok.

Real reefer experiences are often quite different than the BRS video.

I'd personally swap in a new normal carbon block first and see if it removes the total chlorine before buying more expensive blocks claimed to be special for chloramine.

I would like to see near zero total chlorine in the RO input, but do not assume that chloramine degrades RO membranes. I've not seen such data.
 
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FishyFishFish

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Thanks. I’ll swap out the carbon block and keep testing to see how long it lasts. If it only lasts a short time then I’ll have to rethink options as it will become too expensive.

This one is only about 3 months old and I’m guessing has not been used to produce much more than 10 gal per week on average (i.e. 120 gallons or so).
 
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FishyFishFish

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Ok. So I finally got a chance to change out the carbon block and tested the new one. And the result is.......exactly the same as the old one.

Even with a brand new carbon block I am getting 3ppm total chlorine (zero free chlorine) at the waste water output. Product water (after the DI resin) is showing zero chlorine.

What do I do now?
 
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FishyFishFish

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The carbon block is the standard one that comes with the RO Buddie. It comes in a new housing so the block can't be incorrectly seated (it is sealed inside).

I emailed aquaticlife (and their email response time is fantastic) but they have told me that carbon won't remove chloramines and they have advised me to get a 'standard' add on housing and add a chloramine specific filter. This is apparently what they do.

I wish I'd know this when I bought the RO Buddie otherwise I might have gone for a standard RODI system in the first place.
 

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