Your grocery store probably has three types in gallon jugs - spring water, drinking water, and distilled water. The one labeled "drinking water" is RO. I would also keep an eye on Bulk Reef Supply on Black Friday, you should be able to pick up one of their basic RO systems for a good discount. I personally have never used grocery store or lfs water, but have been using an RO system from the start. It has been well worth it and didn't take long to pay for itself.