Why do we use DI on our RO systems.....

[Lousybreed]

I get that we are always told to use RO/DI for any water used for our reef tank. It has me thinking, if a high quality RO unit removes 98% of impurities, and a good carbon filter removes almost all of the "bad" organics, is the DI more of a marketing thing? I mean you sell a RO unit and it lasts years, you sell DI resin and you are getting massive repeat business.

My last question is what are we really worried about getting into our reef water. To mind I think Copper and silica. But after that is there a real reason that we need 0 TDS water? Can you get by with 10 TDS water?

 

[bmbpka]

I get that we are always told to use RO/DI for any water used for our reef tank. It has me thinking, if a high quality RO unit removes 98% of impurities, and a good carbon filter removes almost all of the "bad" organics, is the DI more of a marketing thing? I mean you sell a RO unit and it lasts years, you sell DI resin and you are getting massive repeat business.

My last question is what are we really worried about getting into our reef water. To mind I think Copper and silica. But after that is there a real reason that we need 0 TDS water? Can you get by with 10 TDS water?

to answer the second question, sure you can get by with 10 TDS. Just like you can get by with out QT fish and dipping corals. But it’s an added risk that can quickly crash an expensive investment. So why take the risk and save $50-$100. To me, spending that $50-$100 a year on DI resin is worth it When that water is going to support $5k plus In corals.

there is a lot of crap that goes into our water when producing clean water for human consumption.

 

[andrewkw]

you sell DI resin and you are getting massive repeat business.

If you are giving someone "massive repeat business" then I'd say for sure you NEED the DI. I have pretty good source water and I go through 1 cartridge a year maybe 10 months if I'm making a lot of water for new tanks qt ect. That's $14.99 for the colour change and I could cheap out and buy the non colour change and save $3. I prefer to see, and I typically change before I hit 1 TDS or just after if I'm absent minded.

$20-$30 a year for a lot of piece of mind. Most people probably change at least twice a year, but then that means they have source water that is of poorer quality.

 

[Lousybreed]

Guys I have over 600 gallons in my system and I have a fair amount of dissolved CO2 in my water which rips through DI resin. I am asking if there is data about this. Not someone's feelings. Do we have data that DI is a must for reef success? I get that it is an added insurance policy. But is it needed?

I have high TDS water due to Calcium and Magnesium in my water, but I think we call all say that these two elements are not bad for your reef tank. Based on my water chemistry, 98% of my DI resin goes to removing Ca, Mg, and CO2.

What I fear is that needing DI is an urban legend. Maybe I send out my RO water and get it tested professionally (not ICP) and make my decisions based on that data.

 

[shred5]

Depends on what your tds is.. 2 percent of nothing is nothing but for those who have high tds yes.

Plus you need to know what you are letting through, TDS does not tell you that.

 

[Midrats]

I stopped using DI a while back for the same reason, co2 burning through resin. I'm not interested in setting up some degassing contraption. Without the DI I end up with 4 TDS water. I haven't noticed any difference whatsoever in my tank.

 

[Montiman]

Many systems run fine without DI. WWC doesn't use DI and their systems are what I would call successful. The real answer about weather you need DI revolves around your source water. In my area I have 700-1200 TDS in my tap water and burn through tons of RO filters. I have often wanted to ditch the DI to reduce cost, but I also know that my water is rich in phosphate, silicate, and ammonia all of which the DI removes more than any of the other filters. I have low sediment and chlorine so my pre-filters last a long time. (often 2 years for sediment filters.) but my DI resign only lasts 2-3 months.

If you want to remove the DI first study your source water to find out what the DI is removing.

 

[Randy Holmes-Farley Verified Community Expert]

I get that we are always told to use RO/DI for any water used for our reef tank. It has me thinking, if a high quality RO unit removes 98% of impurities, and a good carbon filter removes almost all of the "bad" organics, is the DI more of a marketing thing? I mean you sell a RO unit and it lasts years, you sell DI resin and you are getting massive repeat business.

My last question is what are we really worried about getting into our reef water. To mind I think Copper and silica. But after that is there a real reason that we need 0 TDS water? Can you get by with 10 TDS water?

If 0.1 ppm of the 10 ppm tds is copper from your pipes, you will wish you used a di.

 

[Gregg @ ADP]

I’ve always maintained that most of us don’t know what our ‘S’ in TDS is actually composed of. Having that analysis done goes a long way in determining to what degree we need to purify our source water.

 

[Gp!]

I am asking if there is data about this. Not someone's feelings. Do we have data that DI is a must for reef success? I get that it is an added insurance policy. But is it needed?

... Snip ...

What I fear is that needing DI is an urban legend. Maybe I send out my RO water and get it tested professionally (not ICP) and make my decisions based on that data.

Can't decide if that is a snarky reply or not

But, TDS is a generic measurement. You can't get a better response than someone's feeling. TDS tells you something is there but not what it is. That level of detail must get the response... Yes you should probably remove it with DI.

You need to do the water testing to determine if you are comfortable with leaving the impurities. It could be uranium after all

 

[Lousybreed]

So I have dove into this topic and my local water and the water of Orlando where WWC gets their water from. Data baby!!! Orlando’s water contains 430% MORE copper (0.6 vs 0.14ppm) and 36% more lead than my tap. My tap water contains more hardness than Orlando’s (17 vs 7) so I will get more Ca and Mg in my RO water. Since I have to dose both Ca and Mg with my calcium reactor this shouldn’t matter. I am thinking about going straight RO!
@Randy Holmes-Farley if we assume 98% rejection rate I would be hovering around 2.8ppb. Thoughts on this level of copper?
Are there any other elements that we need to worry about besides Cu?

 

[Lousybreed]

Can't decide if that is a snarky reply or not

But, TDS is a generic measurement. You can't get a better response than someone's feeling. TDS tells you something is there but not what it is. That level of detail must get the response... Yes you should probably remove it with DI.

You need to do the water testing to determine if you are comfortable with leaving the impurities. It could be uranium after all

Not snarky at all. If you look at my recent post I have provided some data. Waiting on what RFH thinks!!!

 

[Lousybreed]

Can't decide if that is a snarky reply or not

But, TDS is a generic measurement. You can't get a better response than someone's feeling. TDS tells you something is there but not what it is. That level of detail must get the response... Yes you should probably remove it with DI.

You need to do the water testing to determine if you are comfortable with leaving the impurities. It could be uranium after all

And I completely agree TDS doesn’t mean much. It’s the actual elemental composition that matters. Looking into lab testing and I could analyze my real Cu levels for a reasonable amount of money.

 

[Lousybreed]

I stopped using DI a while back for the same reason, co2 burning through resin. I'm not interested in setting up some degassing contraption. Without the DI I end up with 4 TDS water. I haven't noticed any difference whatsoever in my tank.

I see you are from Madison, I am from Sussex. I get about 6-7 TDS from my RO. We all pull from the same aquifer. Thanks for the input!

 

[Montiman]

I might also consider a better membrane. When I used the 1000 gpd producer system from Spectrapure I got 0TDS without DI I kept DI on the system but it lasted forever. A 1000 gpd system may be a good fit for your large tank anyway. Keep in mind WWC is using a higher performance commercial system for their water even though there is no DI.

 

[Sierra_Bravo]

Perform an ICP test on your water straight out of the tap and/or after you run it through your RO. See what you have left going into the tank. Seems simple enough to find out.

 

[Lousybreed]

I might also consider a better membrane. When I used the 1000 gpd producer system from Spectrapure I got 0TDS without DI I kept DI on the system but it lasted forever. A 1000 gpd system may be a good fit for your large tank anyway. Keep in mind WWC is using a higher performance commercial system for their water even though there is no DI.

Great point.

 

[Wolf89]

If you have copper, would tap water purifier not rid it, like it does for feesh water folks?

 

[bmbpka]

I would caution using one water test from the tap to make your decision. Today’s contaminants may be different from tomorrow’s.

For Example, water main breaks 1 block away from your home. After they repair that, they are going to fill that line with chlorine tabs which will ultimately end up in your water. Not to mention that it’s going to stir up other nasty things in those pipes that typically don’t make it to your home. This is why when things like this happen they recommend you boil water. I know DI isnt catching that and it should be caught on pre-filters. Just an example of how your water can change without notice. Water reports are only issued yearly from your local water authority. Things can change on their end and you may not know it until it’s too late.

even if you are exhausting your DI 4-5x a year, it’s $60/year. You stated you have 600 gallon system, why risk all that for $60?

 

[Brew12]

There are enough people using water straight from the tap to prove that reefing does not require RODI. This doesn't mean that all tap water is safe to use in a reef tank. It also doesn't mean tap water that is safe to use won't cause other problems such as algae.
I use it for the same reason I use lab or food grade chemicals for 2-part dosing. I want more control over what goes into my tank.
If you do regular water changes to prevent impurities from concentrating, run GAC to help remove impurities, and have a healthy export mechanism for organics that may be introduced you are more than likely able to get away with tap water or just RO water.
Getting an ICP done on your RO water would be the best way to verify that, although regular ICP testing of your tank can also alert you to a problem caused by bad water.