RO/DI woes

[Hockeynut]

I just bought a new rodi last week set it up and made about 25 gallons. And realized my well wasn't providing enough steady pressure for it to work properly so I ordered a pump to boost pressure. I received my new pump in the mail today and set it up. Now just after 25 gallons my tds meter has the output at 1 could it be possible that my resin is spent after just 25 gallons. It seems I just can't get it right can anyone help

 

[kschweer]

Did you "flush" the system prior to use? Also are you on city water or well water?

 

[redfishbluefish]

....... could it be possible that my resin is spent after just 25 gallons.

Yes! Jersey wells are notorious for CO2 (carbon dioxide), which will chew through DI resin within gallons. The easiest and least expense way to cure this problem is to bubble your water for a day before sending it through the filter.

A simple test is to check the pH of fresh drawn water....and wait a day and measure the pH again. If you see a significant change....it's CO2.

 

[kschweer]

Just re-read your post and noticed you are on well water. This may be your problem. Well water tends to be high in CO2 which can eat through DI resin rather quickly.

 

[kschweer]

Yes! Jersey wells are notorious for CO2 (carbon dioxide), which will chew through DI resin within gallons. The easiest and least expense way to cure this problem is to bubble your water for a day before sending it through the filter.

A simple test is to check the pH of fresh drawn water....and wait a day and measure the pH again. If you see a significant change....it's CO2.

You're quick Paul....beat me to it

 

[Fish Brain]

What is the incoming TDS?

 

[Hockeynut]

15 incoming and I did flush before the fist time and again before this time I do have a well. THis is gonna kill if I go through resin this quIck.

 

[kschweer]

Take a look at this.
http://www.spectrapure.com/faq_p0.htm#calcc02
There's a question and answer about CO2 and RO/DI systems.

 

[Hockeynut]

I just used the co2 calculator on fish friends.com and after testing ph and kh the calculator says my co2 is at 50.4 well over the high range for acceptable co2 content is there any way to lower this without breaking the bank. I'm gonna need to make a lot of water all of the time as you guys all know?

 

[kschweer]

You can run the water through the everything except the DI stage and store in a container with an airstone and let aerate for a day or so and then pump through your DI stage.

 

[Hockeynut]

That sounds easy enough but what sort of pump and pressure should I pump it through the resin ?

 

[redfishbluefish]

This is curable….and you’re almost there having a pump. Kevin (kschweer) just said this…..but I’m going to slightly change what he said.


Here’s what you need to do. Get something to hold water….a 55 gallon drum, Brute garbage can, etc. Put well water into this bucket…..and now bubble it with a simple air pump and bubble stone (as Kevin said). Now since you have the pump, after this water has bubble a day or more, pump it through your whole system….RO and DI. Without the CO2 in the water, your DI should last forever having an incoming TDS of 15.

One more thing, that spent resin you have is relatively easily regenerated.

 

[Hockeynut]

Sounds like a plan thanks Paul ill have to get another drum luckily I have a place that has white food grade drums free, now I just need more space to put it. It can never be easy. Ah I guess if things came to easy life would be boring. Thanks a bunch. Rob.

 

[Zippy69]

This is curable….and you’re almost there having a pump. Kevin (kschweer) just said this…..but I’m going to slightly change what he said.




One more thing, that spent resin you have is relatively easily regenerated.

Paul, I have started to save my di resin for you. I also have well water and my resin lasts for about 250 gal worth, weighed the cost of recharging ( mental trauma from wife ) vs just buy. I will bring it to the next meeting.

 

[Hockeynut]

Paul how do u recharge the resin?

 

[redfishbluefish]

HERE is the recipe for recharging the resin. Simply put, a little soak in sodium hydroxide….a little soak in hydrochloric acid….a little rinse in DI water…….and you’re ready to go. Both are readily found at Home Depot (or a pool store for the HCl)



One note of caution; this author is a little flippant about the use of these two caustic materials. Please handle the sodium hydroxide and hydrochloric acid with great care. Either will burn holes through fabrics and can burn your skin. Sodium hydroxide is very obvious on the skin…it becomes very slippery…while hydrochloric acid, you don’t know you have it on you until after you’re burnt. With either, rinse with plenty of water. Don’t mean to scare you; just handle with care.


One other note of caution; mix the sodium hydroxide in glass or ceramic….slowly adding the solid to the liquid…..it will get very hot. Do not use plastic because the heat will melt or distort the plastic. One more note about plastic….if it was pure plastic, no problem storing either in these jugs. Unfortunately many plastics are made to “degrade,” typically by adding things like starch to the plastic. Over time the plastic breaks down into tiny pieces of plastic. I found out first hand, now with a burn mark on the wood floor in the fish room, that sodium hydroxide accelerates this process. Within a day or two the plastic jug I had for the sodium hydroxide started leaking. I now store it in glass.

 

[Hockeynut]

You are a MADD scientist aren't u. One question how log do I soak in each I have plenty of glass containers and chemical gloves. If it is that easy I would Rather do that then have another 55 gallon drum in my mudroom. I'll just buy more resin so that I can cycle it from being used to being recharged. Is there a limit to how many times I can recharge the resin? Also it's color changing resin will return back to the blue color when it's recharged? Lots of questions I know but I'm new to this DI resin recharging so the more I know the better. Also do I need to change the fluid after each recharge?

 

[Hockeynut]

Thanks again for all your help this is really really helping me out a lot. And could save me a bunch of money in the long haul

 

[redfishbluefish]

One question………

LOL…..I’ll answer all four of your “one question.”

How long do I soak in each?

One hour is more than enough….longer wouldn’t hurt it. It actually is simple chemistry. You have two exchange resins that are mixed together. You need to separate them to “clean” them up. You do this in the first step, where one floats and the other sinks. Once separated, the anionic portion remains in the NaOH. What is happening is that the “nasty stuff” is being replaced by OH ions. (Just the opposite happens when the resin is pulling out the nasty stuff.) Within the cationic resin, you soak it in HCl, and the “nasty stuff” is replaced by the H ion.

Now most people mix these two resins back together to form what is call a MIXED BED resin. Here you use what most have, a single chamber, to run your DI unit. Since I’m a regenerator, I keep by two resins separate and use an old two canister RO water purifier to run the two resins. Now when I have to regenerate, I skip that first step of separating the two resins. I simply soak each in their respective acid or base, rinse, and ready to go. You can see my now duel bed DI unit down low to the left (The old single unit on the right is still hanging there):

I was fortunate to find someone giving away an old RO unit (Thanks Ed). You could also use a BRS Duel Reactor to do the same thing….making sure you buy their resin canisters as well. Since you’re going to be blowing through resin real fast, and you wish to solve this problem by regenerating, I’d suggest you go this route.

Is there a limit to how many times I can recharge the resin?

Unlimited. I explained the chemistry above….pretty simple….no damage to the resin, just a simple exchange of the bad ions with the good ions when you regenerate.

Also it's color changing resin will return back to the blue color when it's recharged?

Yes, the color will return.

Also do I need to change the fluid after each recharge?

I’m going to guess what you are asking is whether or not you need to use fresh NaOH and HCl every time. The simple answer is yes. Since we cannot test how much of the acid or base was consumed in the cleaning process, it’s just simpler to use fresh every time. If you go to a split bed, like I explained above, you will end up using considerably less acid and base….just enough to totally wet the resin and let it soak for an hour.



There, I’ve answered your one question!

 

[redfishbluefish]

One more thing……CO2 actually consumes the anionic resin (plucking out the carbonic acid ions.) So another reason to split the two resins….the cationic resin will not have to be regenerated that frequently.


With all this said about regenerating, I still think your best bet is to bubble your water. If you don’t have the space for a drum, do a search of CO2 bubblers for well water…..I’m sure you could DIY something out of some pipe and an aerator.


Regenerating resin every 25 gallons or so is going to get old real fast.