Reverse Osmosis vs. Deionized Water Filtration – Which is Best?

Water filtration and purification has become a hot topic in the U.S. in light of situations such as that in Flint, Michigan – where high levels of lead had leached into the town's water supply. Many water safety experts have suggested a solution to water safety concerns could be the implementation of extra measures in the home and office, such as integrated water conditioning, filtration and purification systems.

water filtration

However, those looking into water filtration may be overwhelmed by the available choices – from pitchers to under-sink attachments to whole home/office solutions. Similarly, there are a plethora of choices in regard to filtration processes including carbon block filters, reverse osmosis, deionization and more. Due to their efficiency, reverse osmosis and deionization are some of the most commonly selected solutions for water filtration. But what are the differences and which one is right for you?

Reverse Osmosis Filtration

Perhaps the most commonly known of these two options, reverse osmosis was originally designed to filter salt out of ocean water. Now it is one of the most efficient and modern water purification technologies – eliminating up to 99% of common contaminants.

Reverse osmosis works by using a high pressure pump to increase the pressure on the salt side of a membrane, forcing the water across and leaving almost all of the dissolved salts and other contaminants behind in the reject stream. These systems use cross filtration to push the clean water into the regular piping system but allows water to sweep contaminant build-up into the wast water stream – keeping the membrane surface clean.

Reverse osmosis consistently removes:

  • Herbicides
  • rsenic
  • Asbestos
  • Radionuclides
  • Cysts
  • Organic chemicals
  • Chlorine
  • Lead
  • Silicates
  • Pesticides


Deionization systems utilize charged resin beads composed of organic polymer chains. The positive and negative charges on the beads attract undesirable components in the water molecules themselves, producing pure water to push into the regular plumbing system. Deionization produces water similar to distillation.

Over time resins collect materials and lose their charge, requiring the system to be cleaned and regenerated with hydrochloric acid and sodium hydroxide.

Deionization Filters are used to clean molecular impurities such as:

  • Dissolved salts
  • Calcium ions
  • Magnesium ions
  • Metallic ions

The combination of reverse osmosis and deionization can produce water even more pure than distilled. However, for general purification of drinking water, a reverse osmosis filter may be the right choice. Before making a final decision, talk to the water purification experts at Hawthorne Plumbing, Heating and Cooling. Call 702-871-1005.