Malfunctioning RO/DI???

[MechEng99]

Hello! I bought a 2nd hand RO/DI unit made by Coralife today. After installing it under my kitchen sink...several things made me nervous.

1.) I have a 1:1 ratio of DI water to waste water

2.) I'm making about a gallon every 5-10 minutes of DI water (and waste water due to 1:1 ratio)

3.) How will I know if the DI unit needs new resin? The bottom 2/3 is a redish pink color and the top 1/3 is a brownish red.

The person I bought it from thinks it MIGHT be a 75gpd RO/DI unit, but I can't find one made by Coralife with that rating. Also, the person said she had only used the unit for about 200 gallons. Oh, I also live in Ohio (so that should give you an idea of the temperature of the incoming water around here.)

What is the determining factor of the gpd? Is there any way I'll be able to find out for sure?

Also, the sediment filter is a 1micron filter...and the carbon filter is a 5 micron filter, which comes after the sediment filter. That seems counterintuitive to me.

Any and all help would be appreciated!!!!!!

[lesages]

I'm no expert but from what I understand the only foolproof way to make sure a RO/DI filter is operating properly is to test the output with a TDS meter. Testing the raw water will also tell you what % of the TDS it is removing. It seems common for a RO/DI tto make 3:1 waster water to product water so 1:1 would definitly be cause for alarm i think.

[MechEng99]

Yeah, I know to get a TDS meter...I'm just a poor college student...so I was trying to find some cheap alternatives (if any.) :sigh: Thanks for your help though.

Any ideas anyone?

[tkeracer619]

The sediment should be a larger micron.

The membrane could have been replaced with a 75gpd one but I doubt it.

How much did you pay and can you give it back?

Sounds to me like it probably needs a new membrane, DI, and filters........... or in otherwords is just a shell.

Can you post a pic of how its hooked up?

[lesages]

You can pick up a TDS meter for $30. A small price to pay for knowing exactly how clean your water is, no matter what you use.

[MechEng99]

http://reefcentral.com/gallery/data/500/146723RODI.JPG

I paid $86 for it. It came with all of the filters in it, 3 extra sediment filters & 3 extra carbon filters. I'm sure if the person sold me the wrong things I can take it back...I HOPE.

Sorry the pic isn't great...but it was with a cell phone.

[MechEng99]

Uhhh...$30 is like several months of ramen noodles. That might be cheap for you...but my aquarium already lives better than me. But thanks.

[David Grigor]

TDS meter is what you need to truely determine your the DI is exhausted. So either spend the $30 or just keep guessing like you are today........ Color changing resins are okay but what you will find it that even when the color show exhausted you usually have another 3 weeks of good TDS before actually needing changed. IMO: it is a necessary part of owning an RO/DI unit.

[MechEng99]

Thanks David. That answered my question about the color changing resin.

So, any ideas on the 1:1 ratio or how many gpd this thing should really be putting out? Also, what size filters should I be replacing with?

[David Grigor]

Most likely the flow restrictor doesn't match the membrane. If you pop out the membrane it should be labled.

Again the TDS meter will be the best tool to use to verify. Take a TDS reading of your tap, then take TDS reading out of the membrane. Figure out the rejection % rate ( membrane out / tap water ) If it is above 90% then likely things are fine.

[MechEng99]

Shweet. I'll pop out the membrane tonight after I get off work. The more I think about it...the more I think I got hosed on this purchase. Bleh.

Thanks everyone!

[BuckeyeFS]

Another common cause of what seems like excessive purified water ("permeate") production is a membrane that isn't fully seated, or an RO membrane housing that cracked (internally). To tell...sorry...you'll need a tds meter.

Russ @ BFS