The effectiveness of an RO system in removing lime and calcium will depend on the specific model and its filtration capabilities. AÂ reverse osmosis system provides a more comprehensive water purification solution, removing various contaminants, including lime and calcium. If you want cleaner drinking water with the removal of other impurities as well, an RO system might be the better option. Here's more information about two popular options and their efficiency in removing lime and calcium from residential drinking water.