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RODI Woes


jakesweep
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Hey folks. I have a brand spankin' new 4 stage RODI setup from Marine Depot. I'm no expert on setting these things up, but I feel like I've done enough research to be informed. I'm having some TDS issues though.

 

Knowns/Unknowns:

My TDS going in is ~280ppm. I have no pressure gauge. I have 2 different TDS meters spitting out similar readings. My water pressure doesn't seem abnormally lowl, but I do have a booster pump and pressure gauge on the way.

 

Here are the instructions from MD:

1. Remove DI filter

2. Flush the sediment and carbon filters

3. Install the RO membrane

4. Flush for 30 minutes

5. Install DI filter

6. Cook some water and throw out the first few gallons.

7. Profit!

 

Problem is I didn't profit. I dumped the first 5-10 gallons then rinsed the container, ran probably 15 gallons of RODI, tested it, and it showed around 220ppm TDS :( My DI resin is all brown, and the TDS of the water coming out of the RO membrane is ~200ppm.

 

So I did the following:

1. Pulled all the filters

2. Flushed the sediment filter for 5 minutes

3. Flushed the sediment + carbon filter for 5 minutes

4. Emptied all the filter holders and flushed them out

5. Installed the RO membrane

6. Flushed all of them for 2 hours

 

Checked the TDS right after the RO filter and it was at ~180ppm.

 

So I called MD about it and they were pretty confused. They told me to run water through it for a few days(!). Seems like a huge waste of water to me. Is that normal? Any ideas? I don't want to run it for 3 days and waste all that water if I don't have to.

 

 

Edited by jakesweep
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yea that does seem odd. I ran mine for an hour when i first got it and was getting 0 tds. 280tds is pretty high. sounds like maybe the ro membrane was damaged or not stored properly. reguardless, your tds after the ro membrane should 5-10. im wondering if there is a hole in the membrane. while flushing the membrane the tds will read higher. di resin shouldnt be browned out, unless you have different resin. no offense, but maybe something was not installed right or your flush kit is still open?

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No offense taken at all. Things seem to be installed correctly. The membrane is seated; the lid has a good o-ring seal; the tubes all appear to go to the correct places. I think the DI resin is brown since I ran the first batch through the DI filter when I didn't know the TDS was so high after the RO filter. Not so concerned about that at this point though. I really just want to make sure the RO membrane is doing its job.

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37 minutes ago, jakesweep said:

No offense taken at all. Things seem to be installed correctly. The membrane is seated; the lid has a good o-ring seal; the tubes all appear to go to the correct places. I think the DI resin is brown since I ran the first batch through the DI filter when I didn't know the TDS was so high after the RO filter. Not so concerned about that at this point though. I really just want to make sure the RO membrane is doing its job.

hmm. i think you received a faulty ro membrane. it would be very wasteful to run it for 3 days and i have not ever heard of someone having to do that before. or your pressure actually is lower than you think. do you know what psi your membrane is rated for?

Edited by euphylin me
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Ok. So the flow restrictor is one of those that lives inside the 1/4 tube. Not an external unit. I found it sitting inside the box. It must have fallen out of the wastewater tube. Just ran the filter for a few seconds and got a TDS of 30ppm! I'm going to flush the membrane and let it run for a bit then test again. 

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1 minute ago, jakesweep said:

Ok. So the flow restrictor is one of those that lives inside the 1/4 tube. Not an external unit. I found it sitting inside the box. It must have fallen out of the wastewater tube. Just ran the filter for a few seconds and got a TDS of 30ppm! I'm going to flush the membrane and let it run for a bit then test again. 

awesome!

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Thanks for talking this through with me @euphylin me. There's a concept in software engineering called "Rubber Ducking" https://en.wikipedia.org/wiki/Rubber_duck_debugging . I firmly believe in its powers. We're getting close to zero TDS now, and anything above zero I think can be attributed to a borked DI filter since I basically ran tap water through it for an hour. We'll see how it goes.

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Glad you got it sorted out. My tds is in the mid 400s. It is very important that I run the RO membrane for a few minutes before I start sending water to the DI resin or I will use it up fast due to the membrane needing a few minutes to get going efficiently. You should know what your membrane is rated for as far as rejection rate. You should get a TDS if 100-rated reject percentage after your RO only. Your booster pump will improve this.

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The pump I picked up is the AquaticLife Smart Buddie. It auto-flushes the RO membrane which is pretty cool and keeps the pressure right at 80psi. I have high hopes that it will help with membrane longevity and reduction in waste water. I'll do some experimentation before/after comparisons.

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