RODI Not Putting Out 0 TDS

[Schraufabagel]

I've been struggling with red cyano again; and my corals haven't been happy for about a month.

The issue I found is that my RODI membrane is putting our 36 TDS and the DI resin is only polishing it down to 8 TDS. I'm not sure how I missed this. So I've been cleaning out the cyano with water changes only to put that crap water back in. For reference, my city water is 550 TDS

There is still plenty of good DI resin left in the 4th stage, but I wonder if I should add a second DI resin stage. I am using the RO/DI Buddy booster pump which puts my 100 GPH unit at ~ 90 PSI, so that shouldn't be an issue. Is 36TDS out of the membrane good, or is that still too high?

 

[Woodyman]

I've been struggling with red cyano again; and my corals haven't been happy for about a month.

The issue I found is that my RODI membrane is putting our 36 TDS and the DI resin is only polishing it down to 8 TDS. I'm not sure how I missed this. So I've been cleaning out the cyano with water changes only to put that crap water back in. For reference, my city water is 550 TDS

There is still plenty of good DI resin left in the 4th stage, but I wonder if I should add a second DI resin stage. I am using the RO/DI Buddy booster pump which puts my 100 GPH unit at ~ 90 PSI, so that shouldn't be an issue. Is 36TDS out of the membrane good, or is that still too high?

Using your numbers your membrane would only be rejecting at ~93% so time for a new RO membrane.

A new membrane should get you down around ~10 TDS out of the membrane at ~98% rejection.

 

[Woodyman]

A second DI stage would help as well, but if your DI resin still appears to have usable life (based on color change) you may be better setting up 2 additional DI housings and running 3 stages of DI (cation, anion, mixed bed).

 

[Schraufabagel]

Using your numbers your membrane would only be rejecting at ~93% so time for a new RO membrane.

A new membrane should get you down around ~10 TDS out of the membrane at ~98% rejection.

I just replaced the membrane a month or two ago. And the membrane for that I only had for 6 months. I switched that one because I was getting about 50 TDS out of that one yet. Could there be another issue causing it?

 

[Woodyman]

I just replaced the membrane a month or two ago. And the membrane for that I only had for 6 months. I switched that one because I was getting about 50 TDS out of that one yet. Could there be another issue causing it?

Could be, @flyfisher2 had a similar experience, but his TDS was not as high as yours. His problem came down to a bad RO housing that was allowing bleed through into his RO water.

How old is your unit? Specifically the RO housing. How is it stored (inside, outside)?

 

[Schraufabagel]

Could be, @flyfisher2 had a similar experience, but his TDS was not as high as yours. His problem came down to a bad RO housing that was allowing bleed through into his RO water.

How old is your unit? Specifically the RO housing. How is it stored (inside, outside)?

The unit is around 8 months old. It’s a Bulk Reef Supply 4 stage 100 GPH. The pre filters were replaced around 3 months ago as well

 

[Woodyman]

I just replaced the membrane a month or two ago. And the membrane for that I only had for 6 months. I switched that one because I was getting about 50 TDS out of that one yet. Could there be another issue causing it?

Some other things it could be are:

Are membranes being properly seated in the housing?

Are you monitoring for chlorine breakthrough? Chlorine will kill a membrane

What size sediment are you using and how frequently is it changed?

 

[hllb]

I am asking this question, because I have done this before. Do you have your DI canister facing the right direction? The first time I refilled mine, I put it in upside down and saw similar numbers to you (reduction in TDS, but not 0).

 

[Woodyman]

The unit is around 8 months old. It’s a Bulk Reef Supply 4 stage 100 GPH. The pre filters were replaced around 3 months ago as well

So more than likely not a damaged housing, but who knows with shipping. Being a newer unit my next assumption would be chlorine destroying your membranes prematurely.

Have you ever monitored or checked chlorine content of your RO feed water before? (Post sediment/carbon prior to RO housing).

 

[Dbichler]

Do you have a flush kit with tds in the 500s that would be an extremely important factor in ro membrane lifespan.

 

[Schraufabagel]

For reference, here is how I have everything connected.

Source water -> Pre filters -> rodi buddy -> PSI gauge and membrane intake -> waste line to RODI buddy then to drain, and membrane output line to TDS reader input 1 and DI stage -> DI resin output to TDS reader input 2 and RODI buddy -> lastly the line runs into my collection bucket with a float valve

 

[Schraufabagel]

Do you have a flush kit with tds in the 500s that would be an extremely important factor in ro membrane lifespan.

Supposedly the RODI buddy flushes the membrane for me according to the manual. I removed the according pieces it directed me to as well

 

[Schraufabagel]

I am asking this question, because I have done this before. Do you have your DI canister facing the right direction? The first time I refilled mine, I put it in upside down and saw similar numbers to you (reduction in TDS, but not 0).

I have the DI canister seated with the arrow facing up

 

[Woodyman]

Do you have a flush kit with tds in the 500s that would be an extremely important factor in ro membrane lifespan.

He said he had the BRS 4 stage, I don't have a BRS branded setup so I'm unsure if it has a flush, but I assumed BRS included this with their models. Maybe I'm mistaken.

 

[Schraufabagel]

So more than likely not a damaged housing, but who knows with shipping. Being a newer unit my next assumption would be chlorine destroying your membranes prematurely.

Have you ever monitored or checked chlorine content of your RO feed water before? (Post sediment/carbon prior to RO housing).

I have not, but I will check what is put out from the pre filters before it goes to the membrane

 

[LuizW13]

Following along. I might learn something. Good luck OP.

 

[Woodyman]

Supposedly the RODI buddy flushes the membrane for me according to the manual. I removed the according pieces it directed me to as well

What where your numbers like when you initially started using the unit vs now.

 

[Schraufabagel]

What where your numbers like when you initially started using the unit vs now.

When I start the unit the output from the membrane shows 280 and the output from the DI stage shows around 10. After running the unit for about a minute is when it drops fully to the 36 and 8 respectively

 

[Dbichler]

Supposedly the RODI buddy flushes the membrane for me according to the manual. I removed the according pieces it directed me to as well

I don’t think that’s actually possible without manually switching it. Flush kits force all the pressure on the membrane and barely anything goes past to the di. Hence flushes the tds out of the ro membrane.

 

[Schraufabagel]

First image is from the BRS RODI system manual (I have the plus system) and the second is from the RODI buddy manual. Those are the prices I removed as directed