Need explanation please?

[Norman Fenske]

I have been told that its not advisable to use a DI filter okay but why?? Not discounting anyone I just want to know why. I called the manufacturer of the RO and was told they heard of it vaguely but since they have been making RO units nobody has complained I also went to the LFS and they a larger system then mine and they use the DI filters. All I want is to make sure I set it up correctly.

 

[gerald]

If your source water is hard or has high mineral content, then a deionizing filter placed BEFORE the R.O. unit will help the R.O. membranes to last longer before they get plugged up with minerals. If your source water has low to moderate mineral content, then DI is unnecessary. Disclaimer: I have soft tap water and don't use either DI or RO, so my advice is just based on what i've read and learned, rather than personal experience.

 

[Norman Fenske]

The unit I have 1st the sediment 2nd the carbon 3rd the RO membrane 4 and 5th DI. I was told the DI long term will break down the silicone in an aquarium?? I have looked into this and cannot find anything remotely related. I called the Manuf. of the RO and was told they heard of it but since they have been making RO's they have not had anyone complain concerning this. My LFS has had their system hooked for quite awhile and they have no issues. SO figured I would ask.

 

[gerald]

Somebody with a big mouth and attitude probably had a tank (on a crooked stand) leak after buying a DI unit, and proceeded to rant extensively wherever he could find an audience about how the DI water caused his tank seams to fail. Sounds like a wacky theory to me.

 

[Mike Wise]

One reason is that DI cartridges are expensive. They cannot be recharged without using caustic chemicals, so most manufacturers don't allow it, but recommend you replace it instead. If you do use DI units you 'polish' the R/O water even more, but once you add it to an aquarium with its biological load the minimal amount of hardness lowered by the DI unit is a waste of money. As Gerald wrote, you could lower the mineral content passing through the R/O membrane by using D/I first, but periodical use of a back-flush unit is much more economical in the long run. Back-flush units push R/O water backwards through the membrane and remove elements trapped in the membrane. If you want to use DI in an aquarium it's not a problem, just a waste of money IMHO. If, however, you need pure water for analytical purposes, like my wife does to do gravimetric tests (she's a metrologist, no not a meteorologist), then DI is the way to go. "It's all about the money!"

 

[Norman Fenske]

Ok I understand but the way my system is set up it goes sed, carbon. RO membrane and 2 DI.if I understand correctly for now I might as well use it but once its used up unless I reroute and have the DI first I would be better off not using it or finding another type of filter to replace it with correct ??

 

[dw1305]

Hi all,
I'm a rain-water user, but we have <"Elga DI units"> in all the labs at work. Like Mike says the DI cartridge just polishes the water, usually after it has been through the RO membrane, and removes the remaining ions via ion exchange. A lab grade DI unit will produce water at below one microS conductivity, and then there are ultra-pure units where you will measure resistance, rather than conductivity.

Is it worth it? Not for me, not even as an RO unit. I live somewhere it rains a fair amount, I have hard tap water, an environmental conscience and a water meter.

If I couldn't use rain-water I'd keep small Lake Tanganyika cichlids in our tap water.

cheers Darrel

 

[Mike Wise]

My location gets less than 18"/45cm of precipitation (rain and snow) per year (high plains desert) . My tap water source is snow melt from the Rocky Mountains and is relatively soft. So Darrel & I have different needs. I use R/O to make blackwater for blackwater species. Otherwise my fish live and breed happily in my tap water. My R/O unit has a place for a DI cartridge, but I just don't use it. It's empty other than water that simply passes from the R/O membrane to to outlet.

 

[dw1305]

Hi all,

I use R/O to make blackwater for blackwater species. Otherwise my fish live and breed happily in my tap water. My R/O unit has a place for a DI cartridge, but I just don't use it. It's empty other than water that simply passes from the R/O membrane to to outlet.

I don't keep any black-water species, mainly because even our rain-water has some carbonate hardness. With our hard tap water (about 650 microS and 18dKH) you get a lot of "waste" water and relatively short membrane life from an RO unit.

As Mike says an RO unit can make sense for people with soft water, because you have a low waste water ratio and long membrane life.

cheers Darrel

 

[Linus_Cello]

If you have a dehumidifier or have an central air conditioning unit, could you use the water created from them as soft water?

 

[dw1305]

Hi all,

If you have a dehumidifier or have an central air conditioning unit, could you use the water created from them as soft water?

I think you can, a lot of people say that the water will contain aluminium, copper etc. but I'm not convinced about this.

cheers Darrel

 

[Mike Wise]

If the dehumidifier has copper coils I'd be cautious. Test the water with copper sensitive fish like tetras, naked scaled catfish like pimilodelids, of loaches first.