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Crazed Fish Whisperer
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Discussion Starter · #1 ·
Well, I have had my RO/DI unit for about 4 years, and no matter how I dial it in, or replace the cartidges, I can't get a TDS reading below 34 anymore. So it was suggested the the membrane is starting to go bad. If it is the membrane going bad, it was also suggested that in some cases, it is almost cheaper to just buy a new unit.

What I have now is a 75gpd Oceanus 4 stage: Micron, Charcoal, DI resin, RO membrane. I went to their website and it is down for revamping.

What RO/DI units do you guys use or recommend? Any brands to stay away from? Any good brands to consider?
 

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air water ice, spectrapure or the filter guys are all reputable companies that sell quaility units right out of the box.

In fact....before you replace yours, as I dont know anything about it I would call spectrapure or the filter guys and see if they can get you into a new 75 gpd filmtec membrane to get you back to zero without dropping the cash on a entire new unit
 

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Have you tested the water after RO or just the final product after DI? I would confirm that the RO membrane needs to be replaced. A full DI resin can actually increase the TDS and I have also gotten bad DI cartridges in the past.

As others have said you shoulf be able to get a filmtec membrane for $50-60.
 

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I wouldn't buy a whole new unit, that's a waste of money. If your ro/di uses standard filters, they are not very expensive to replace. I just got a higher capacity membrane for less than $100 and picked up some inexpensive prefilters and carbon blocks. Don't forget to change those too!
 

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Crazed Fish Whisperer
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Discussion Starter · #8 ·
Hmm...very good info. I will need to look to see how I can test the DI water. Right now, all I test is the final product. (have changed the cartridges a few times now), so unless I have gotten several bad cartridges, I think it is the membrane. Is it easy to figure out the tds reading before hitting the RO membrane? Is it as simple as detaching the water line going in to it and filling a cup?

Thanks for the info and the links!
 

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Is it easy to figure out the tds reading before hitting the RO membrane? Is it as simple as detaching the water line going in to it and filling a cup?

Thanks for the info and the links!
If you have a hand held TDS meter then yes. Disconnect the line going from the carbon filter to the RO membrane and take a samp-le. Then disconnect the line going from the the RO into the DI and see what you get there. You are sure that the lines coming out of the RO housing are correct, correct? Just want to make sure that somewhere along the way the product and waste water lines weren't swapped, feeding bad water into the DI.
 

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Crazed Fish Whisperer
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Discussion Starter · #11 ·
If you have a hand held TDS meter then yes. Disconnect the line going from the carbon filter to the RO membrane and take a samp-le. Then disconnect the line going from the the RO into the DI and see what you get there. You are sure that the lines coming out of the RO housing are correct, correct? Just want to make sure that somewhere along the way the product and waste water lines weren't swapped, feeding bad water into the DI.
I have never disconnected any lines going to or from the RO membrane, so that should all be correct still. I will run the test as you described to see what my readings are at on either side of the membrane. Thanks!
 

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Crazed Fish Whisperer
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Discussion Starter · #12 ·
Ok, took the readings and I am confused. The cartridges, like the others arn't that old but... this is what I get.

Tap water: 221
After water has gone through the micron and charcoal filter and is on it's way in to the RO membrane: 245
Water leaving the RO membrane on it's way to the DI Resin: 22
Water leaving the DI Resin to the container: 31

And this was after doing 4 tries on each stage to help ensure accuracy. Thoughts?
 

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That makes it look like the DI is spent and actually starting to leach ions back into the water.

Yes, overall, you need a new membrane. Membranes normally have a life of 3-5 years.

How much water do you discard after changing pre-filters?
 

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Crazed Fish Whisperer
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Discussion Starter · #15 ·
wharyat - I have the drain line going directly in to the floor drain. As for the good line, I maybe discard a gallon after changing the filters.

tellycoleman - ok..I didn't think of letting the unit run for a while before testing. will that make a difference?
 

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Jeremy - did you get your system squared away?

Sounds like you were reading TDS creep water with your meter.

A agree with the above posts re no need for you to get a whole new system.

Let's start with some accurate TDS readings of your tap water, RO water, and then DI water. Let the system run for 5 mins before you take samples of the RO and DI water. Use a squeeky clean glass sample jar (e.g., a drinking water glass) for this. Rinse three times with the water you are about to sample.

Russ @ BFS
 
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