RO vs RO/DI?

[360º]

anyone know what the difference is and what the advantage or disadvantage of each system is?

 

[melosu58]

RO water uses filters and a RO membrane that the water goes through. A RO/DI unit uses filters, RO membrane and a Deionized unit.

This excerpt from Liveaquaria on the one I use explains it all.

"The 4-stage Maxxima RO/DI takes the full size RO to a higher level of filtration. The Maxxima is an excellent selection for reef enthusiasts and other serious aquarists, especially those who live in areas with exceptionally high levels of phosphates in their tap water. Includes: TFC (Thin Film Composite) membrane, carbon and sediment pre-filters, mixed-bed deionizing post-filter, with clear canister housings. The post deionizer takes the small percentage of contaminants that the membrane could not remove and filters this to greater than 99.9% pure."

 

[360º]

so whats necessary for a reef tank? the the deionizing unit necessary?

 

[melosu58]

If it was me I would use a RO/DI unit. I do use one. I use the coralife maxxima but they have cheaper versions on Ebay. You could get away with just an RO unit but it wont be as good as a RO/DI.

 

[360º]

If it was me I would use a RO/DI unit. I do use one. I use the coralife maxxima but they have cheaper versions on Ebay. You could get away with just an RO unit but it wont be as good as a RO/DI.

so what added benefit does the deionizer give you? what does it remove from the water that the RO doesnt?

 

[mr_X]

so what added benefit does the deionizer give you? what does it remove from the water that the RO doesnt?

the rest of the stuff you don't want.

 

[Kurt_Nelson]

RO units will remove about 95% of the "stuff" from the water. If 95% pure is good enough, then you can stop at that point. But if you want 100% pure water, the DI part will remove the remaining 5% of "stuff" to give you 100% pure water. Without the DI part, you could still be getting nitrates, phosphates, etc... in your water - just in much smaller amounts than you originally had.

 

[uscamaro]

you can find a 50-75 gpd (gallon per day) on ebay for $100. I bought a 100 gpd for $140

 

[cmor1701d]

The RO membrane will remove 90% - 98% of the total dissolved solids (tds) from the tap. The DI takes that to 100. So if your tap water has a tds 200, you will have 4 -20 tds water. The DI portion takes that to 0.

 

[cabezon]

If you are going to buy and set up the unit it would behoove you to go with the DI. I had an older RO ojnl6y that I added a DI to for very little cost. There is no good reason not to have di.

 

[mellowyellow]

Ok Cmor I have a huge question. Aquarists aren't supposed to use distilled water because it is tooooo pure. Now, everyone at AA champions RO water. Isn't it the same thing Pure is Pure.

 

[Kurt_Nelson]

... Aquarists aren't supposed to use distilled water because it is tooooo pure....

You might be confusing freshwater with saltwater. I've never kept freshwater, but I think "pure" water for them is not a good thing. They need the stuff in the water to make it hard, the right pH, etc. With a saltwater tank, you're adding a salt mix and getting all that stuff back anyway. So to start with pure water, you insuring that your water will be the same everytime and you're not introducing excessive nutrients from your tap.

 

[360º]

You might be confusing freshwater with saltwater. I've never kept freshwater, but I think "pure" water for them is not a good thing. They need the stuff in the water to make it hard, the right pH, etc. With a saltwater tank, you're adding a salt mix and getting all that stuff back anyway. So to start with pure water, you insuring that your water will be the same everytime and you're not introducing excessive nutrients from your tap.

so does RO/DI lower the PH to neutral and the hardness to Neutral?

 

[Floyd R Turbo]

RO/DI leaves you with nothing but H2O, so you will really not be able to measure the pH very well (since pH is a measurement of the H+ ions, and the water is de-ionized) and there is essentially no buffer at all (KH=0). It is a "clean slate" to which you add the salt mix, which provides everything that needs to be there.

 

[360º]

oh ok thanks for the info

my tapwater right now comes out at PH 8 and KH 180

 

[Kurt_Nelson]

RO/DI leaves you with nothing but H2O, so you will really not be able to measure the pH very well (since pH is a measurement of the H+ ions, and the water is de-ionized) and there is essentially no buffer at all (KH=0). It is a "clean slate" to which you add the salt mix, which provides everything that needs to be there.

Yup yup. Even though you *can* measure the pH of pure water, and you'll get a number, it's useless to do so. Since there is so little of what you're measuring to arrive at a pH value, any little mistake in the testing or any contaminant that might be left in the vial from a previous test is going to skew the results more than they normally would.

 

[360º]

so what type of RO/DI unit do you guys recommend?

are the ones off ebay any good?

AQUA REEF RO DI REVERSE OSMOSIS PUR WATER FILTER SYSTEM on eBay.ca (item 380306867611 end time 17-Jan-11 22:07:50 EST)

 

[mr_X]

they are basically a bunch of plastic cases that hold filters. it's the extras that set them apart. like pressure gauges, built in T.D.S. meters..etc.