What is the difference between R.O water and Deionized water?

drizcol

Member
What is the difference between R.O water and Deionized water? which is better I found deionized water at the lfs for $.50 a gal. where is a better source for this water?
 

sly

Active Member
They are really like apples and oranges. RO water is water that has been passed through a membrane under high pressure. The pores in the membrane are so small that only pure water can pass through and bigger particles like lead and silicates are left behind. It is like an extremely fine filter.
DI water is water that has passed through a DI reaction chamber. Here, dissolved particles in the water are chemically removed through a process called deionization. For example, when something like sugar dissolves in a glass of water, the sugar becomes electrically or ionically attached to the water molecules. Simple RO filtering can not remove many ionically dissolved substances. But because DI'ing is a chemical process, DI'ing water cannot remove many of the non
ionically dissolved particles.
If you could only chose one or the other, I would chose RO water. Most of the contaminates in water are free floating anyway and using a RO filter will generally give you the cleanest water (over just plain DI water).
If you want the best water you can get, you need water that has been both RO filtered and DI treated. Here you remove all free floating/suspended particles and all ionically disolved substances.
DI water has no chlorine (dissolves ionically) and RO water has no copper (retained in a suspension)... You need both to have good water.
 

drizcol

Member
wow thanks for the info! I think I will just stick with ro water, I have no idea were to get ro and di water. I bet its pricey though!
 

lepete

Member
Originally Posted by DRIZCOL
wow thanks for the info! I think I will just stick with ro water, I have no idea were to get ro and di water. I bet its pricey though!
Nahhh... You'll pay about a few pennies more for RODI than just RO. It is very inexpensive to hook a DI unit to an RO unit. And, you probably can make 1000+ gallons of DI water before having to change the DI resin.
If your LFS says it has DI water... I am willing to bet it is really RODI. Water is expensive when a DI unit is hooked straight to city water (w/o an RO unit).
Homemade RO is probably $0.10/gallon
Homemade DI is probably $0.40/gallon
Homemade RODI is the price of RO + a few pennies...
 

drizcol

Member
well all the LFS's that I called around here sell just RO water. The One store that said they have DI told me that they only use DI water because RO water removes things that the fish need. He said with DI water you dont have to add anything back into the water. with RO you do.
Sounds to me like he does not know what he is talking about.
the store that has DI water sells it for $.50 a gal. The stores that have RO water say its $1+ per gal.
 

xrayman

Member
If you want to mix your own salt you can go to wal-mart supercenter and get ro water for 33 cents a gallon.
 

littlebuck

Active Member
well walmart water isnt always good. I did a water change with there water and came up with red slime. I called them and they said the guy that checks it didnt go there the one month so the store just wrote something on there to say it was tested. SO watch out with there water. And that water is just purified with RO nothing with DI. Just watch out with there water yes for .33 a gallon its good but dont know if the water is good unless you check it with a TDS. Well good luck likemyself im gonig to just get a RO/DI unit and take the hit now but dont have to worry about anything wrong with my water again. Good Luck
 

xrayman

Member
Yeah i have searched and read some of those stories to,and there are lot of them out there that have no problems also.I switched from using Distilled water 2 months ago and so far so good.Going to keep an eye on it though.Thanks for that info.
 
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