RO filter question

[birdy]

This is so frustrating, I replaced my sediment, carbon and DI filters the first of Jan, I also bought a TDS meter finally so I would know when to change the filters. I have recently been fighting a small patch of cyano in tank, with little luck. I tested my RO water and it was still 0, I replaced my sediment filter but didn't replace the carbon thinking it should last another couple of months. Well today the RO/DI water is at .003 TDS, I tested it for ammonia and Nitrite (with freswater test) and they are both 0, the thing is the water smells horrible, that was my only clue, smells like dead fish. Obviously it is time to change the Carbon filter and I am going to go ahead and change the sediment again, but I don't get what could be causing the smell if I test .003 TDS and ammonia and nitrite are 0.
Just by testing the water I would think it was fine, but since it smells like that I don't think I should use it.

 

[birdy]

I do understand that, but I guess my question is, what could be causing the smell in the water.

 

[birdy]

nope- tap smells fine, it is just too weird.

 

[johnny5]

What about your RO membrane itself? Have you flushed it in awhile? Thats basically the only filter that has not been changed right?
My rodi unit has 6 filters: 2 sed's, 1 carbon/di, RO, some other filter after the ro, and the final filter for taste/smell (this would be suspect #1 if you have not changed it).
First id try smelling the waste water, if its doesn't smell then its something on the other side of the RO filter. I susect its the final filter if you have one but it could be the ro membrane itself.
One other thing, is your output hose above the gas trap on your sink? If not you may be getting some bad gas/water thru the waste water line. To test that, just disconnect it and run the waste water into a bucket. You will want to flush the ro and run it for awhile to see if the odor disappears.
If all else fails, I'd take it apart and smell each part to find the source. You can clean the filter containers and hoses with hot tap water (NOT YOUR FILTERS THO, hot water will screw them up).
Thats about all I can think off :notsure:

 

[birdy]

Thank you Johnny those were very good suggestions, I took my unit apart and figured out which section was bad, it was my DI unit which is weird because it is suppose to last for 700-1000 gallons. So I tested the TDS of just the Membrane (and the sediment and carbon filters) well it was like 125 so obviously I need a new RO membrane (the thing is only a year old!). I am seriously thinking I need to just get a whole new unit.

 

[johnny5]

No problem.
Yep, the filters alone can cost more than a packaged deal it seems.
I bought an aquasafecanada reef model off ---- for under a hundred (75gpd membrane). Its been working great since I got it a month ago, thats not really long enough to give it 2 thumbs up yet tho but it seems to be well made.
Glad you found the fishy filter tho! :hilarious