Is the DI in RO/DI worth the extra $50?

[Anonymous]

I'm looking at options for producing RO water and the 4 stage RO/DI option is $50 more expensive than the 3 stage RO. What difference does that DI make? Is it worth the extra $50?

Bear in mind I'm not planning an SPS-dominated tank, but will want to keep a few if I can, in addition to LPS, softies etc. If the RO filter does all I need I'd like to save the money, but for want of a few dollars more, I don't want to start my next tank with a bit of a handicap that I will regret.

 

[Ben1]

I used to use a double DI RO unit and I always had to change the first one just like normal. I would move the second one to the first position and refill the other cartridge for the second chamber. I dont think it made a difference, I know it made me lazy and once I saw the first DI was exsausted I would sometimes wait untill the second was wearing out and think that made the second get used up even faster then normal. I just felt when I used this two DI stage system I was goign through more resin then ever. I don't reuse my resin though. If I was regenerating resin http://reefkeeping.com/issues/2008-09/nftt/index.php then I think it might better. I probably should be saving my resin for regen.

 

[Anonymous]

MY DI takes my TDS down to 0. Without it, my three stage RO unit gets me to TDS of 15.

Hard to say what still in there and whether it would affect your tank. It was worth the extra few pounds for me (not that my tank looks so great).

 

[Len]

I have the same results as Mitchell on two RO units. RO only brings TDS to about 10-15ppm. The addition of a DI takes it to zero. When the TDS begins to rise, I change out the carbon, micron, and DI carts and the TDS go back to zero. I only replace my RO after a few replacements of the other cartridges.

 

[Ben1]

Oops I thought you were asking about a double DI vs. a single. I wouldnt run an plain RO unit, I need that DI. I change my DI twice before I change the carbon and micron. I only change the membrane once every two yearsish.

 

[Anonymous]

Thanks guys. I thought there was a reason this was probably worth it, but I had only the RO unit last time, so wasn't sure what the difference was. $50 added to my budget...

 

[Anonymous]

do you know the TDS of your tap water? My water here in NYC is 30-35 TDS coming out of the tap. I ditched the RO altogether, and just buy bulk DI resin. Sure, i go through the DI resin quickly. I use the refillable cartridges and I get about 100 gallons out of a change. I like it because it's faster to fill the bucket and I don't waste 4 gallons to get 1 gallon of clean water.

If you can't get bulk DI, then it doesn't make a difference. I get a cubic foot of it from resindepot.com and it lasts me almost a year.

B

 

[Anonymous]

I think you have your answer already. Basically, it has to do with your water TDS. If it is good, then don't bother, other, like me with 600ppm, you really don't expect the RO to do much, so we are forced to pay that $50.

 

[Anonymous]

I'll probably go for the RO/DI option, as I will be buying the TDS meter at the same time as I buy the RO/DI unit, so I won't know the TDS of my tap water until I've got both!

 

[livingstone]

It has been said this way--the RO is simply one of the pre-filters for the DI section. So, though, percentage wise, it doesn't reduce the TDS figure as much as the RO unit, it is the fundamental section of this type of water purification system.

 

[Ben1]

You may want to get a dual TDS meter, the inline type. This way you caan check TDs after the membrane and after the DI.

 

[Anonymous]

Good explanation Livingstone, thanks.

 

[Anonymous]

I have the same results as Mitchell on two RO units. RO only brings TDS to about 10-15ppm. The addition of a DI takes it to zero. When the TDS begins to rise, I change out the carbon, micron, and DI carts and the TDS go back to zero. I only replace my RO after a few replacements of the other cartridges.

I do the same. My tap water TDS starts at 360ppm.

 

[Anonymous]

I have a pressure meter inline with my RO unit, when my pressure drops that's when I know it's time to change the Sediment/Carbon filters as they're gunked up. I have multiple inline dual TDS meters but I'm too lazy to check them half the time I also run 4 seperate DI canisters (I bought a refill kit once that had more than the refill it had the tubes they stuff goes in, so I simply run 4 DI resins), this is good too can I can simply wait for the colors to change and typically the first one in line will do so first, so I swap that one out (in reality I just move the rest towards the front and the new one goes in the back)... a bit more complicated sure, but I'll always have nice resin ready to go

 

[Old Man Of The Sea]

I found that using two HI-S DI cartridges, comparing to two DI cartridges I have far greater water quality and the difference in price is only $14 more for HI-S DI cartridges, it does give me peace of mind. The water were I now live, is the worst i ever seen, and upon making ready the reef tank, I will also be adding a second carbon cartridge with a booster pump.

Buddy

 

[Ben1]

I wonder what type of resin is in the HI-S cart that makes it absorb more silicates?