RO/DI pumping out phosphates

Hey everyone,
So, I'm hoping someone can help. I have a specrtapure 90 GPD RO/DI filter system. I also have an inline TDS meter attached. I had been making water for about a year and a half with no issues, and I noticed that my TDS meter always showed a 0 (zero) value for my output water. However, I recently had a major algae bloom (again), and so I checked the output water and sure enough, not a lot, but there were some phosphates in it (like .25). My TDS still showed as 0. Well, my resin looked close to being finished and so I changed out all the filters (except the RO Membrane) and started it back up. Well, now my TDS meter shows as 798 as my input and 700 as my output. Now this seemed incredibly high (both in and out). Sadly I can't remember what my input TDS level is usually, but it's not 0, so I typically didn't care since the output was showing as 0. The production is also very slow. I'm wondering a few things:
1. The water is extremely cold these days out here (I'm in Colorado) - could this be affecting the TDS meter and if so, how?
2. I know the colder water slows down the production too, but not sure if this is in fact the cause for that as well. Thoughts on ways to check that?
3. You think I should get a handheld TDS meter as well? Have any/all/none of you had success with the inline ones?
3. Should I try flushing the membrane (I need to buy a kit if I want to do that) or should I replace it at this point? I have never flushed the membrane, so not sure at this point, if it's just toast or not.
4. What tips are there for extending the life of the membrane (other than flushing) with these Spectrapure systems? Should it be installed at an angle for example, so that when not in use the water doesn't drain out and dry out the membrane (I had one like that before that recommended that)? Or things like that?

Thank you all in advance. Your help and knowledge has been and continues to be invaluable to me.

 

First toss the inline and invest in a real handheld TDS meter that is temperature compensated. Good examples are the HM Digital TDS-3, TDS-4TM, AP-1 and COM-100. While I own two of the dual inlines I never even turn them on anymore, they suck. I have a COM-100 and a AP-1 and rely on the COM-100.

You cannot accurately measure contaminants in ultrapure waters, I don't care what any vendor tells you, test kits and $50 meters will not do it. You only friend is a good handheld TDS meter or a conductivity or resistivity meter, don't believe anything else.

Cold water is far superior to warm or hot water! Cold water is more dense, higher viscosity, so it treats better and the TDS will be lower than warmer water. DO NOT try to warm the water or blend jhot and cold, it will raise the TDS and contaminants. If you want higher GPD invest in a RO booster pump, higher pressure makes membranes work even better.

Flush kits are a waste of money, they supposedly flush the waste side of the membrane but do nothing for the treated side of the membrane where TDS creep is the issue. If you want bang for your buck invest in a DI bypass valve, maybe $10-$15, to flush the TDS creep out before it hits the DI resin.

 

Thank you DesertRat for the response!
I tend to believe the test kit because I went from no algae to raging algae again and top off water from this filter system is the only change in the environment at this point.
So, it sounds like at this point your advice is that I should get the new TDS meter, and a new membrane and see what I get? Or are you thinking that I should get the meter and then verify the TDS before I replace the membrane and/or get this DI bypass to flush things? Couldn't one accomplish the same thing as the DI bypass by simply removing the resin from the DI stage and run normally? And I'm not sure I understand how bypassing the DI stage could flush the membrane anyway.
I actually run the filter at 90 psi as I've heard that higher pressure is better. Is that too high or bad do you think?
I keep having issues here, so I want to make sure that I'm not doing something wrong.
Thanks again for the help!

 

FYI, "many organics" is on the list of things a TDS meter will not detect...

What is TDS? by Randy Holmes-Farley - Reefkeeping.com

 

I would get the handheld TDS meter and check your tap water TDS, RO only TDS and final RO/DI TDS before I did anything else. I would also check the waste TDS just for reference.

If your RO only TDS is really 798 and RO/DI is 700 as you say, you have either a bad membrane, bad housing or the membrane is not installed properly. I would not order a new membrane until you know what the problem. Thats one of the problems with an inline, it is dedicated to two places, usually RO and final RO/DI TDS and you need 3 TDS readings to troubleshoot the system including the tap water.

Phosphates are weakly ionized and may not register well on low end TDS meters but you can assume if you have TDS present that is one of the culprits if you have it present in your tap water. If you are measuring 0 TDS with a good meter you can feel confident your treated water is good though. Myself I use the COM-100 as it is 10x more sensitive than the others and reads TDS down to tenths of a part or can be used in conductivity mode.