Differences between RO and RO/DI

[badgergoth]

I'm starting to get together the kit for my new 20 gallon newbie tank, and looking at RO units, they seem to come in two types - smaller RO units which probably produce around the kinds of volumes I'll need, or much larger RO/DI units which will mean I'll be drowning in RO.

What I was wondering is (a) what does the deionizing bit remove that the osmosis bit doesn't in RO/DI. (b) Is there a marked difference in coral success between using RO and RO/DI?

If the difference is significant, then I'll just build a boat and float around on all the excess water, but I don't want to spend a whole bunch more for not a lot of benefit (if that's the case).

Cheers

 

[Anonymous]

Both RO and RO/DI use the same amount of water. You do not waste more water by going with RO/DI. Important thing is to get one with the correct GPD rating (gallon per day of filtered water).

For some location, you really need RO/DI since RO along is not sufficient if the water is really hard. The extra DI step remove the ions (Na, Cl, Mg, etc.) that managed to come thru the RO membrane.

One good thing is that you can always add DI to RO-only filter later if you found that the RO is not enough. The upgrade cost between 0->RO/DI and 0->RO->RO/DI is very little so for many people, they get the RO first and see how well it goes.

 

[badgergoth]

Ahh yeah, it was the GPD that I was relating to - getting a small unit which does RO/DI seems near impossible. RO/DI seems to be the domain of high output units.

But if I can add DI to a small scale RO unit at a later date, that would solve the problem.

Thanks

 

[ChrisRD]

If the difference is significant, then I'll just build a boat and float around on all the excess water, but I don't want to spend a whole bunch more for not a lot of benefit (if that's the case).

I'm not sure I understand why you would have excess water. The GPD rating refers to the rate at which product water is produced. In other words, a membrane rated for 100 GPD could produce a little over 4 gallons per hour, but you don't have to produce any certain volume per day. Just make as much as you want and then shut the unit off. A higher GPD unit will just get you your water faster.

Also, keep in mind that in your home installation, unless you've got extremely high water pressure at your home, or you're going to use a booster pump, you won't get anywhere near the rated production from the unit. Generally the membranes are rated at higher pressures and warmer water temperatures than most of us would be running them at in our homes (and both of these things will effect production rate of the unit). You may very well get half or less of the rated performance from the unit.

HTH