View Full Version : RO/DI Problems

Reef Freakz
12/19/2013, 08:41 PM
I have an Aquatic Life 4 Stage 100GPD unit. I replaced the sediment filter, the carbon block, and I bought vacuumed sealed resin for the LFS and refilled the DI cartridge. I did not replace RO membrane. I am getting 50 TDS tap inlet, 4 out of RO membrane, and 4 out of DI outlet. The DI isn't doing anything. I have checked it several times, taken it out, even flipped it upside down to try and get a different reading and still get 4 TDS outlet.

4TDS/50TDS= 80% Does this mean I should replace the membrane since I am not getting 95-98%? If I replace it won't I get down to 1 TDS in Theory?

Shouldn't the DI remove the other 4 TDS?

What should I do next?

12/19/2013, 09:23 PM
Have you tested with another TDS meters? Could be as simple as a defective meter.

Reef Freakz
12/19/2013, 09:24 PM
No I just got this TDS meter in this evening new.

12/19/2013, 09:25 PM
When you replaced the resin did you pack it in as tight as possible? If it is loose it is not nearly as affective. What is your tap water pressure? If it is below 45 PSI you may want to consider getting a booster pump to increase the efficiency of the RO membrane. Do you flush the RO membrane regularly? Doing so will increase efficiency and prolong its life. You should get at least two years from a good RO membrane, most likely three years if you flush it regularly.

12/19/2013, 09:31 PM
That would be my next thought. Pack you DI if it isn't and try again. I run my RO at approx 40 psi and have 0 TDS output.

On the other hand 4ppm TDS is not that bad. But I understand wanting better.

Reef Freakz
12/19/2013, 09:32 PM
Flushed it two different times for 5 minutes each and the RO outlet dropped to 1 TDS both times. Once I started producing again it climbed back to 3 TDS again within a minute or two of running on the DI outlet.

I packed it in tight. The cartridge had a white foam 1 inch thick donut in both top and bottom which fit tightly on top of the resin. I don't have a pressure gauge but its excellent water pressure.

I bought this unit used an don't have a good idea of the amount of water it has filtered.

Reef Freakz
12/19/2013, 09:36 PM
The unit looks like it is running every bit of a 4 or 5 to one water split. I can fill a 44 gallon can in 9 hours so its putting out the 100GPD.

I am trying to get the best I can. I don't have a drop of water in my tank and I'm anxious to get it started but I want to do this right. Would you keep trying for better or consider 4 TDS good enough?

12/19/2013, 09:49 PM
Hmm, the rejection rate for your membrane is 92%, if the meter is correct. I thought many of the 100 gpd membranes were only rated for 90% or so at normal household water pressure. What is the brand and model of the membrane?

If the DI membrane is any good, I suspect that the problem might be with the TDS device. I'd get a second opinion, personally.

12/19/2013, 09:51 PM
I agree with bertoni on the TDS meter as to weather or not to go with the 4ppm, I would.

Reef Freakz
12/19/2013, 10:04 PM
This is an Aquatic Life RO/DI 4-Stage Deluxe 100GPD unit. I assume its the same RO membrane that came with the unit.

The DI resin looks like it might be BRS refill. Its was at my LFS in a vacuum pack. I just refilled it last night.

I have run 40+ gallons each of the last two nights. I just dumped it for the second time. Like I mentioned I just flushed the membrane using the flush valve twice for 5 minutes each. I started it for the night and have run about 3-4 gallons and it is now holding at 2 TDS. I'm at a loss for what to do the get better numbers unless I buy another meter to check the one I just received.

12/19/2013, 10:12 PM
IMO it would be a waste of money to buy a new membrane if youe getting 2 TDS. Also a lot of those meters can be off by + or - 2 to 3 TDS

12/19/2013, 10:46 PM

12/19/2013, 11:20 PM
2 TDS out of the membrane is okay. 2 TDS past the DI cartridge would imply to me that the DI isn't working. I don't know which membrane comes with that product, so I can't help there. The numbers you're giving vary so much I wonder whether the membrane was installed properly.

Buckeye Hydro
12/20/2013, 03:15 AM
Sounds like your membrane is ok. How are you measuring the TDS of your DI water? Inline meter? Handheld? If handheld, are you letting the system run sor a few minutes before you take your DI water sample? What are you using for a sample container?


Buckeye Hydro
12/20/2013, 03:22 AM
Some info on loosely packed resin -

You can pack mixed bed resin as loose as you'd like - that's not really an issue. The problem is that in a loosely packed upflow cartridge the mixed bed resin will fluidize and the anion beads and the cation beads will separate based on their weight/specific gravity. Now you have small separate bed treatment and it won't be as effective as when the beads were mixed.

It's the separation of the beads that causes the issue.


Buckeye Hydro
12/20/2013, 03:24 AM
Once you get this issue solved, there's some other things to think about with that used system. But we can leave that for another discussion...

Reef Freakz
12/20/2013, 05:45 AM
I'm measuring with a dual inline meter. It ran all night and filled my can and held at 2 TDS. Its 2 out of the RO and 2 out of the DI as well.

Buckeye Hydro
12/20/2013, 05:46 AM
Are the probes on that meter rotated properly?
http://i224.photobucket.com/albums/dd293/BuckeyeFS/Instructions/CorrectProbealignment.jpg (http://s224.photobucket.com/user/BuckeyeFS/media/Instructions/CorrectProbealignment.jpg.html)

12/20/2013, 07:43 AM
This may be a stupid question, but are you sure you bought mixed anion/cation resin from the LFS? Separate anion and cation resin can certainly be purchased, and if you have just anion or just cation resin, you're not going to get to 0 TDS.

Buckeye Hydro
12/20/2013, 07:44 AM
Ha! Good thought.

Reef Freakz
12/20/2013, 08:26 AM
Yes I checked probes and they are installed properly. Mixed resin was amix of gold and blue resin so it looked like mixed resin. My DI chamber on this unit has inlet and outlet within an inch of each other near the bottom of the chamber which seems odd. Is that typical?

Buckeye Hydro
12/20/2013, 08:33 AM
Do you have the system that is in the black box with blue caps on the top?

Reef Freakz
12/20/2013, 09:10 AM

Reef Freakz
12/20/2013, 09:13 AM
Aquatic life deluxe 100 gpd.


Buckeye Hydro
12/20/2013, 09:22 AM
Then yes - that is how those systems are set up. I'm not a big fan of those systems, in that they do nothing that a more typically configured system does, they just wrapped a brittle plastic box around everything. And they don't have a pressure gauge. And unless you take the box apart you can't install an inline tds meter correctly. Oh well.

One other thought. Are you missing the rubber gasket at one end of your DI cartridge? Do you have your DI cartridge installed upside down?


Reef Freakz
12/20/2013, 09:40 AM
There is no gasket at the bottom. It's just the plastic housing with a ring of triangular holes which allow water into bed. Top has typical large rubber gasket. Should there be some type of seal or gasket in the bottom of this unit or on the bottom of the cartridge?

Buckeye Hydro
12/20/2013, 10:01 AM
Nope - just on the top end of the cartridge. So sounds like you are ok.

Have you tried switching the in and out probes on your meter to see if the readings change?


Reef Freakz
12/20/2013, 10:17 AM
No I haven't. I will try that. Good idea.