Confused about RODI Chlorine testing

[FishyFishFish]

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?

 

[Biglew11]

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.

 

[FishyFishFish]

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]

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?

 

[DaddyFish]

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.

 

[FishyFishFish]

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]

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

Can Thin Film RO membranes tolerate chlorine?

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. 
   
   
   Rating:
   91%
   Miscellaneous
   PENTEK CHLORPLUS CARBON BLOCK
   Starting at: $23.99
   
   Choose Options
   
   
2. 
   
   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%.
   

 

[Randy Holmes-Farley]

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.

 

[FishyFishFish]

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).

 

[FishyFishFish]

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?

 

[Biglew11]

How long did you flush the system. The old water will still contain chlorine. Let it run about 30minutes to an hour before testing.

 

[FishyFishFish]

It's now been running for several hours and I have just tested again (although this time directly after the carbon filter). Same result.

 

[Biglew11]

is the carbon block seated properly? water could be bypassing the block inside the canister. a brand new block should remove all the chlorine from the water.

 

[Randy Holmes-Farley]

What carbon block?

 

[FishyFishFish]

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.

 

[homer1475]

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).

No chlorine or chloramines in my water, and it's relatively clean(22incoming TDS at the tap). When I started back up I got the RO buddie as it was cheap.

Even at 10G a week, my ro buddie only lasted about 150 to 200 gallons of water before the carbon, sediment, and DI resin filters needed to be replaced. Many years ago I switched to a BRS unit that uses standard sized houses and filters. I replace with spectrapure filters and get well over 1000 gallons before needing to replace any filters.

The RO buddie works, just not very well made, and the filters don't last very long either(just look at the size of the filters in comparison to a standard sized filter and you'll understand why they do not last very long).

 

[FishyFishFish]

Just to close this off.

I bought a standard sized add-on cylinder and added a BRS 1 Micron Carbon filter to my RO Buddie. My chlorine now tests at zero after the carbon stages.

I will keep testing to see how long this block lasts, but I can confirm that the RO Buddie carbon cartridge does not filter out chloramines.

 

[Randy Holmes-Farley]

Thanks for the update!

 

[AirIck]

Just to close this off.

I bought a standard sized add-on cylinder and added a BRS 1 Micron Carbon filter to my RO Buddie. My chlorine now tests at zero after the carbon stages.

I will keep testing to see how long this block lasts, but I can confirm that the RO Buddie carbon cartridge does not filter out chloramines.

I’m a newb and concerned I may need to replace something as well. How do you test between stages to know what to replace or do you replace all filters at the same time? I have a 5 stage RODI system. My TDS reads 0 on “out” but I noticed my pressure is now 80 where it used to be 90. My corals have also been struggling for 2 weeks and my parameters are the same so I’m concerned I may have chlorine in my water?