For all of you peeps out there filling up your water bottle at the DI tank. 
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:
Deionized water lacks minerals normally found in water which have beneficial health effects. Calcium and magnesium, in particular, are desirable minerals in the water.
Deionized water aggressively attacks pipes and storage container materials, leaching metals and other chemicals into the water.
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.
Use of DI for cooking can lead to loss of minerals in food into the cooking water.
At least one study found ingestion of deionized water directly damaged the intestinal mucosae. Other studies did not observe this effect.
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.
Morale of the story: DI water= good for windows, bad for drinking lol
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