Is It Safe to Drink Deionized Water?

Scientist holds a beaker under a water spout.
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Drinking a small amount of deionized (DI) water usually doesn't present health issues, but there are several reasons why drinking large volumes of DI or drinking deionized water as your only source is dangerous.

Deionized water is water from which ions have been removed. Ordinary water contains many ions, such as Cu2+ (Copper ion minus two electrons), Ca2+ (Calcium ion minus two electrons), and Mg2+ (Magnesium ion minus two electrons), These ions are the most commonly removed using an ion exchange process. Deionized water may be used in laboratory situations where the presence of ions would cause interference or other problems.

It is important to note that deionized water is not necessarily pure water. The purity depends on the composition of the source water. Deionizing does not remove pathogens or organic contaminants.

Why Drinking Deionized Water Is Unsafe

Aside from its unpleasant taste and sensation in your mouth, there are good reasons to avoid drinking deionized water:

  1. Deionized water lacks minerals normally found in water which provide beneficial health effects. Calcium and magnesium, in particular, are desirable minerals in the water.
  2. Deionized water aggressively attacks pipes and storage container materials, leaching metals and other chemicals into the water.
  3. Drinking DI may lead to increased risk of metal toxicity, both because deionized water leaches metals from pipes and containers and because hard or mineral water protects against absorption of other metals by the body.
  4. Use of DI for cooking can lead to loss of minerals in food into the cooking water.
  5. At least one study found ingestion of deionized water directly damaged the intestinal mucosae. Other studies did not observe this effect.
  6. There is substantial evidence drinking DI disrupts mineral homeostasis. Longterm use of deionized water as drinking water may cause organ damage, even if additional minerals are present elsewhere in the diet.
  7. There is evidence that distilled and DI water are less likely to quench thirst.
  1. Deionized water may contain contamination in the form of bits of ion exchange resin.
  2. While deionized water made from distilled or reverse osmosis purified water may be pure, deionizing nonpotable water will not make it safe to drink!

If You Must Drink DI

Experts have tasted deionized distilled water and it does not taste good. According to them, it feels strange or prickly on the tongue, but it did not cause any burns or dissolve tissue in their mouth. If locked in a lab storage room with the choice between other solvents, DI, or heavy water, the deionized is the least dangerous, but there are a couple of ways to make it safe:

  • Let the DI react with air. The water readily picks up ions from the atmosphere, quickly turning it into the ordinary purified water.
  • Don't let the deionized water run through pipes or glassware that has been encountered nasty chemicals. In other words, don't give the DI a chance to leach toxic metals or chemicals from its container.
  • Let the water settle and avoid drinking the portion at the bottom. Although not a proven fact, it is possible that any ion exchange resin beads would sink to the bottom of the container and it is better not to take the risk. An alternative would be to run the DI through a filter. Don't use a bleached coffee filter or paper towel, however, or you'll likely leach more dioxin into the water than remove potentially dangerous resin.

Reference

World Health Organization. Frantisek Kozisek. Health Risks from Drinking Demineralised Water. National Institute of Public Health, Czech Republic.