Standing in front of the shelf, drinking water and distilled water look like the same product at similar prices, and they are not. One is sold to be drunk and keeps its dissolved minerals; the other is sold as a process water with almost nothing left in it. Buying the wrong one wastes money in one direction and scales up an appliance in the other.
What you are paying for in each jug
A jug labeled drinking water is water made fit to drink. It may be filtered municipal water with minerals adjusted for taste, and it is meant for the glass and the cooking pot. Distilled water is a process specification: it has been boiled and the steam condensed, which strips out nearly all dissolved solids and leaves water that tastes flat. Neither is a premium version of the other, so read the label for the word rather than for the price or the design of the bottle.
Match the water to the job
Distilled goes into machines that heat water or spray it through a fine opening: steam irons, garment steamers, room humidifiers, CPAP reservoirs and lead-acid batteries. Drinking water goes in the glass, the coffee maker and the pan. The reason is scale. As the USGS explains, hardness is dissolved calcium and magnesium, ranked as soft at 0 to 60 mg/L as calcium carbonate, moderately hard at 61 to 120, hard at 121 to 180 and very hard above that, and those minerals bake out onto every hot surface.
The cheaper end of this decision
If you are buying drinking water by the jug every week because the tap tastes wrong, the arithmetic is against you: bottled water costs a household far more over a year than treating the supply once. Test what comes out of the tap, find out whether the complaint is chlorine, hardness or something specific, and then buy the piece of equipment that answers it. Our best filter for drinking water guide sorts that out by problem rather than by brand, and the distilled jug can go back to the iron.
Questions people ask about drinking water vs distilled water
Can I drink the distilled water sold for appliances?
It is safe to drink, though it tastes flat, and some jugs sold for irons and batteries are not bottled to food handling standards. Check the label before you pour a glass.
Which one should go in a humidifier?
Distilled. Mineral in ordinary drinking water turns into white dust on the furniture and scale on the element, which is exactly what distilled water avoids.
Is drinking water just tap water in a bottle?
Often it is treated municipal water, yes, sometimes filtered and remineralized for taste. That is legal and disclosed on the label if you read the small print.