ro without di

[carsonc]

I have been using an RO unit that has a sediment filter a carbon block filter and the membrane unit. The tank is about 1 1/2 years old. I know I overfeed but I do 18 gal water changes weekly, the total volume is 75 gal. I have been having a small problem with hair alga and macro alga growing too much.
I just got a TDS meter and it says the tap water is 345 and the RO output water is 14. This sounds about right to me.

The question is could the tds of 14 be enough while doing 24 % water changes every week to cause the extra growth of the alga.
Do you think it would help the alga problem to add a set of DI filters after the RO unit?

Thanks Carson

[Randy Holmes-Farley]

I just got a TDS meter and it says the tap water is 345 and the RO output water is 14. This sounds about right to me.


Yes, that sounds fine. :)

The water is very likely fine to use. The only concern that I'd have is if there is chloramine in the tap water then there may well be substantial ammonia in the effluent.

In any case, I wouldn't guess the water is part of the algae problem.


These articles may help:



Phosphorus: Algae’s Best Friend
http://www.advancedaquarist.com/issues/sept2002/chem.htm

Nitrate in the Reef Aquarium
http://www.advancedaquarist.com/issues/august2003/chem.htm

Iron Oxide Hydroxide (GFO) Phosphate Binders
http://reefkeeping.com/issues/2004-11/rhf/index.htm

[carsonc]

Thanks for the reply Randy.
The tap water here does have chloramine in it, I was told that the carbon block filter would remove the chloramine.
If the carbon is not enough would adding the DI filters help to remove it.
I read the articles and it sounds like I will be converting my sump into a macro farm.
I have tested for ammonia but have never got a reading (after the tank was cycled).
Carson

[Randy Holmes-Farley]

The tap water here does have chloramine in it, I was told that the carbon block filter would remove the chloramine.

Nope. It breaks it apart into ammonia and chloride, as described in the article above. Try measuring the RO effluent for ammonia (before and after adding salt; salt mixes sometimes have some as well).

Yes, a DI will take out the ammonia. :)

[chem_fun]

I believe that DI should take everything else out.

I have been told by my supplier that 15 ppm coming out of the RO will yield about 300 gallons...give or take a few.

ebay - aquasafesystems

Only thing I changed on their set up was the puncture valve. I didn't want to punch through a pipe, so I went to home depot and got a T. I took the cold water feed off, added the T....connected the cold water back to the sink and added the RO to the T. Presto, I can move my RO/DI if needed.

[carsonc]

Thanks for the reply Randy and Chem_fun
When looking at the DI filters there are different types.
I would think that it would be better to go with 2 units, one for the cati and one for the ani, The mixed resin sounds like it might not work as well or as long as seperate units. Although it might be better to have 2 of the mixed resin inline that way there would be a backup If one does use 2 units should one be before the other (ani - cati or cati - ani) in the flow from the output of the RO.
Also some of the units use filters that you replace the insert while others can be rejuvenated ??. There also seems to be one that you fill with the different resins. What is the preferred way to go.

[chem_fun]

Being as Randy has a few more letters behind his name, we'll see if he agrees.

I don't see a need in our hobby to spend the money on separate cation and anion chambers. My personal set up (as I want 0 TDS water for chemistry labs) I have an inline TDS meter after the first mixed bed resin and a second 'newer' DI chamber after the TDS meter.

The TDS meter is a dual model, and I have the second TDS meter after the RO unit. A hand held meter can be used to test the tap and final RO/DI waters. In this way I can easily check the water in 4 locations. I can tell the effectiveness of my RO membrane, easily tell if the first DI chamber is spent, and then rotate in a new DI tube.

While I haven’t had an RO membrane long enough to need a replacement, I have been told that upon proper replacement of the prefilters it will last many years. At the inexpensive cost of the prefilters and the mixed bed resin...this seems like a pretty good set up for my use.



I don’t believe that there is an order to the cation and anion resins…but I’m not sure.

The rejuvenation process, however, takes a strong acid and strong base. And then the means to fully neutralize the ‘cleaning’ chemicals once the resin has been recharged. DI Resin clumps together and is a bit slippery. Refilling the tubes would seem to be a pain to me. Its worth any extra spent to just be able to swap out the cartridges. Though, I guess it does depend on your need.

[Randy Holmes-Farley]

The only reason to think the separate resins are better is when you want to recharge them yourself. I've been using a single mixed bed on the Spectrapure system for many years, and it works just fine. :)

[carsonc]

Thanks again guys
I belive I will use 2 of the mixed bed cartridge type units.
With 2 identical units I will only need to stock 1 type of cartridge and like Chem_fun said add a tap between them to check the operation of the first one. I do not have a tds monitor so I will just have to check it manually with my tds pin point type meter.
I would assume any thing >= 1 would mean the cartridge is used up.
Thanks again
Carson

[Randy Holmes-Farley]

Yes, that is reasonable. I describe a bot of how to use TDS for such a purpose in this article:

What is TDS?
http://www.reefkeeping.com/issues/2004-04/rhf/feature/index.htm

from it:

"

7. If you are using a TDS or conductivity meter to monitor the performance of an RO membrane, then the measured value should drop by at least a factor of 10 from the starting tap water. So, for example, if the tap water reads 231 ppm, then the RO water should be less than 23 ppm. In many cases, it will drop much more than that. Less of a drop than a factor of 10 indicates a problem with the RO membrane.

8. If you are using a TDS or conductivity meter to monitor the performance of an RO/DI system, then the measured value should drop to near zero. Maybe 0-1 ppm. Higher values indicate that something is not functioning properly, or that the DI resin is becoming saturated and needs replacement. However, that does not necessarily mean that 2 ppm water is not OK to use. But beware that it may begin to rise fairly sharply when the resin becomes saturated. Do not agonize over 1 ppm vs. zero ppm. While pure water has a TDS well below 1 ppm, uncertainties from carbon dioxide in the air (which gets into the water and ionizes to provide some conductivity) and the TDS meter itself may yield results of 1 or 2 ppm even from pure water. "

[carsonc]

Thanks Randy
Carson

[Randy Holmes-Farley]

You're welcome.

Happy reefing. :)