ice made from reverse osmosis (”RO”) water produces cleaner, clearer and better tasting ice cubes because most of the contaminants are removed from the water. So, just because water is purified by a certain process, (in this case, reverse osmosis), has no bearing on whether you can make ice.
Sizing a reverse osmosis system is critical when you have multiple outlets, especially if one or more is an under-the-counter ice-maker. Most residential reverse osmosis systems are 24 to 50 GPD (gallons per day), which is not nearly enough for such an ice-maker. Additionally, production is reduced whenever the water temperature is below 77 degrees F, and whenever the pressure is below 60 PSI. In the real world, a 50 GPD reverse osmosis system in the Midwest may produce 20-25 GPD, when the demand may be up to 150 GPD
Carbon filtration is a marvelous method for removing chlorine, chemicals, pesticides and numerous other contaminants, providing it is applied properly. For example, you would not want to put a carbon filter on water that is microbiologically unsafe. This would require chlorination (with adequate contact time) ahead of the carbon filter, or some other method such as ultraviolet or ozonation to inactivate the bacteria.
In times past, most RO systems were rated at 12 to 50 gallons per day. That simply means that if it ran continuously for 24 hours it would produce that amount of water. However, in the Midwest where water temperatures are lower than 77 degrees Fahrenheit; the production is about half the rated capacity of the system. Today, many homeowners are opting to connect their kitchen sink, vegetable sink, pot filler, wet bar, multiple ice-makers and the master bath to the RO system. This necessitates the usage of higher capacity RO systems (75 to 300 GPD) along with larger storage tanks and delivery pumps, which boost the pressure.