RODI Unit Help

[CFish4812]

Hello,

I have a 150 GPD water saver RODI unit. It was in storage for 3-4 years while I wasn’t in the hobby. I am now starting again.

I replaced both 75 GPD membranes and all filters. I started making water again but can’t get my TDS under 16-18 prior to DI. My source water is 180-190. The membranes are firmly inserted and there are no leaks that I can see. I have a booster pump and get 80 psi.

I thought I must’ve received bad membranes since my old membranes consistently made 1-2 TDS water prior to the DI stage. I ordered new membranes and installed them a few days ago.

I’ve flushed the unit for hours and made probably 50 gallons of water without the DI stage trying to get the TDS down and hoping that the membranes need more time to hydrate and break in but I’ve had no luck. The TDS actually went up to the 20-25 range.

Did I ruin my unit by not cleaning it when I took it out of storage? Do I need a new unit? I want to start my tank but am concerned I’ve messed up something. It is 0 TDS after RODI but I’m concerned I’ll burn through DI rapidly.

Can anyone help me? I’ll answer any questions or provide more info.

Thank you.

 

[Saltyreef]

What brand of membranes are you using?

 

[CFish4812]

What brand of membranes are you using?

DuPont FilmTec

 

[EricR]

Hopefully you get better answers but since you mentioned "not cleaning"...
If you just want to spend some time trying something, you could sanitize the system using Buckeye Hydro's instructions here:
Sanitize RO System

I recently did that (just to do) for the first time ever on a 4 year old RODI unit and noticed a 1-2 TDS drop (after RO membrane) with no other changes and my unit had been running for 4 years, never stored.
*could've been coincidence but maybe you'd actually notice some improvement, dunno

 

[CFish4812]

Hopefully you get better answers but since you mentioned "not cleaning"...
If you just want to spend some time trying something, you could sanitize the system using Buckeye Hydro's instructions here:
Sanitize RO System

I recently did that (just to do) for the first time ever on a 4 year old RODI unit and noticed a 1-2 TDS drop (after RO membrane) with no other changes and my unit had been running for 4 years, never stored.
*could've been coincidence but maybe you'd actually notice some improvement, dunno

Thanks for sharing. I wonder if I do this if I have to replace all the prefilters again. I hope not. It’s just frustrating. I had no problems at all when I first got started. 1-2 TDS and 0 after DI for years. I had three tanks back then.

 

[EricR]

Thanks for sharing. I wonder if I do this if I have to replace all the prefilters again. I hope not. It’s just frustrating. I had no problems at all when I first got started. 1-2 TDS and 0 after DI for years. I had three tanks back then.

You don't have to replace anything. Just basically remove all filters/media to sanitize and put back after.
That's why I suggested as just something to try if you wanted to.

 

[CFish4812]

You don't have to replace anything. Just basically remove all filters/media to sanitize and put back after.
That's why I suggested as just something to try if you wanted to.

I did end up cleaning with bleach. I made sure the pre filter section is clean and flushed. We’ll see if it helps at all tomorrow.

 

[Tangdora]

You water pressure is probably the problem. You that dupon membrane says it only rated for max efficiency at 50 psi.

 

[CFish4812]

You water pressure is probably the problem. You that dupon membrane says it only rated for max efficiency at 50 psi.

Hi thanks for your advice. I’ve always used this pump with all the old membranes. If I don’t use it then my psi is only 35-40 and I was told that’s too low.

 

[Marco_99]

I know it sounds stupid, but can you post a picture of your whole unit and show exactly what resins or filters you changed?

 

[CFish4812]

 

[CFish4812]

my unit is shown above. I replaced the sediment filter and both carbon blocks. The carbon blocks are 1 micron rated for both chlorine and chloramines. The membranes were also replaced and are DuPont FilmTec 75 GPD in a water saver configuration.

The DI is currently not hooked up while I’m troubleshooting the high tds

 

[Marco_99]

So where are the other two DI resin canisters lol.

 

[CFish4812]

So where are the other two DI resin canisters lol.

They’re not connected because the TDS after the membrane using all new filters and membranes is nearing 30. After DI it is 0 but I don’t want to exhaust the DI resin while troubleshooting the problem.

My old membranes were 1-2 TDS before DI and 0 after. There is a big performance difference and I’m trying to figure out the issue.

 

[Marco_99]

What is your water source? Is it well water?city water? Since you haven’t used this thing for three or four years, I mean to expect the water sources to be exactly the same readings as back then, I don’t know if that’s plausible. I don’t really know that much about the scientifics of it but if you’re reading zero coming out of all your filters with your resins hooked up I don’t think there is much to investigate. The unit is doing its job. Sounds like a change in your source water maybe

 

[CFish4812]

What is your water source? Is it well water?city water? Since you haven’t used this thing for three or four years, I mean to expect the water sources to be exactly the same readings as back then, I don’t know if that’s plausible. I don’t really know that much about the scientifics of it but if you’re reading zero coming out of all your filters with your resins hooked up I don’t think there is much to investigate. The unit is doing its job. Sounds like a change in your source water maybe

City water that uses both chlorine and chloramines. Yeah I guess maybe something changed that the ro unit is struggling to remove. I don’t know.