Which chlorine/chloramine RO/DI should I buy?

[Randy Holmes-Farley]

Well, I often use it for freshwater and do near-total water changes for QT/hospital tanks. I'm not sure what the minimum detection level of chlorine using the color wheel is but I wouldn't be confident it's below 0.05 mg/L. And I wouldn't bet my life that it's below 0.1 mg/L either.

OK, I get that. I'd want a much lower level there too.

 

[KStatefan]

But wastewater is what washes the contaminants from the membrane, so doesn't that entail it coming in contact with it?

I'm not trying to be difficult, just wondering if I really need to be taking a water sample prior to the membrane.

Are you just taking the sample to test for chlorine? If so you are fine with that location.

 

[Randy Holmes-Farley]

I agree. Wastewater is the thing to test to see if the membrane is getting exposed to chloramine.

FWIW, I only had two RO/DI systems in 20 years, and neither ever had an RO membrane replaced. But testing with a Hach kit did show 0.02 ppm chloramine in the wastewater (which contacted the membrane). Apparently, that level, assuming it was real, never cause problematic damage.
Here's what I detected witha Hach CN-70 kit:

Tap water:
pH ~9
Total Chlorine: 0.4-0.5 ppm one day, 0.08 ppm on a second day.
Free chlorine: <0.01 ppm (effectively all of the total chlorine was chloramine)

RO Reject water:
Total Chlorine: 0.02 ppm
Free chlorine: <0.01 ppm

Final RO/DI water:
Total Chlorine: <0.01 ppm

 

[EeyoreIsMySpiritAnimal]

I agree. Wastewater is the thing to test to see if the membrane is getting exposed to chloramine.

FWIW, I only had two RO/DI systems in 20 years, and neither ever had an RO membrane replaced. But testing with a Hach kit did show 0.02 ppm chloramine in the wastewater (which contacted the membrane). Apparently, that level, assuming it was real, never cause problematic damage.
Here's what I detected witha Hach CN-70 kit:

Tap water:
pH ~9
Total Chlorine: 0.4-0.5 ppm one day, 0.08 ppm on a second day.
Free chlorine: <0.01 ppm (effectively all of the total chlorine was chloramine)

RO Reject water:
Total Chlorine: 0.02 ppm
Free chlorine: <0.01 ppm

Final RO/DI water:
Total Chlorine: <0.01 ppm

Thanks again. This post is very helpful.

 

[EeyoreIsMySpiritAnimal]

Are you just taking the sample to test for chlorine? If so you are fine with that location.

Yes, and for clarification, the location I test from is prior to the water entering the membrane housing (before it touches any part of the membrane/ premembrane layers at all). My thinking was that if chlorine can damage the membrane, I want to test the water right after the last carbon to be sure it's not exposed to any chlorine.

Sounds like it may be overkill but I'll still test there since I have things plumbed that way.

 

[Miami Reef]

Yes, and for clarification, the location I test from is prior to the water entering the membrane housing (before it touches any part of the membrane/ premembrane layers at all). My thinking was that if chlorine can damage the membrane, I want to test the water right after the last carbon to be sure it's not exposed to any chlorine.

I also have mine plumbed this way. I need a way to rinse the carbon filters BEFORE it comes in contact with the membrane.

 

[Miami Reef]

I'd try them on tap water, RO/DI waste water (= water in front of the RO membrane) and on the RO/DI final effluent.

Let the RO/DI run for a bit so you are checking representative water, since water sitting in or near the carbon block when it is off gets a much longer exposure.

Done.

The second from the top on the strip is total chlorine.

The third from the top on the strip is free chlorine.

Seems like I’m just dealing with a little chloramine and a tinyyyyy bit of chlorine, and my current carbon blocks are doing a fine job at eliminating it. I don’t remember which carbon blocks I purchased before. I’m going to check and post if I find out.

 

[Miami Reef]

Edit. Looks like I’m using the same carbon block as I just ordered: BRS Universal Carbon Block Filter - 1 Micron

Good thing I got more of those. I’m going to just change them both when they start showing chloramine, instead of just changing one every time I change the sediment filter. There’s no way to test individual carbon blocks in my RO set up.

 

[Randy Holmes-Farley]

Good to hear. This is what I recommend folks do before buying extra expensive filters: see if ordinary ones are adequate.

 

[Miami Reef]

Good to hear. This is what I recommend folks do before buying extra expensive filters: see if ordinary ones are adequate.

I thought the BRS 1 micron universal filter WAS the extra expensive one. $18.99 per each without shipping and tax sounds pretty expensive for a carbon block to me. Disclaimer, I know pretty much nothing about carbon block pricing.

Anyway, I think I’m just going to use 1, and change it out as needed. Using 2 together just seems more wasteful to me. Maybe I’m wrong, but that’s just what it feels like.

 

[Randy Holmes-Farley]

I thought the BRS 1 micron universal filter WAS the extra expensive one. $18.99 per each without shipping and tax sounds pretty expensive for a carbon block to me. Disclaimer, I know pretty much nothing about carbon block pricing.

Anyway, I think I’m just going to use 1, and change it out as needed. Using 2 together just seems more wasteful to me. Maybe I’m wrong, but that’s just what it feels like.

Ah, ok, I didn’t realize it was their chloramine one. I haven’t looked at carbon block brands in quite a while.

 

[Buckeye Hydro]

To clarify this "pre" or "post" membrane issue.

Let's introduce a bit of jargon.
The blue filter about 1.8" in diameter and 12" long that we all call "a membrane" is actually better referred to as an "RO Element."

An RO Element is made up of multiple layers (often referred to as leaves). Only one layer of each leaf is actually the semipermeable RO membrane. These multiple leaves are attached to the central stem, and then wound around the stem in a spiral fashion.

So concentrate (often erroneously referred to as "waste water") has been through the Element - from one end to the other, but it has not gone through the RO membrane layer.

Russ