In chemical and biological laboratories, as well as industry, cheaper alternatives such as deionized water are often used alongside distilled water. However, if these alternatives are not sufficiently pure, distilled water is used. Where exceptionally high purity water is required, double distilled water is used.

Distilled water is also commonly used to top off lead acid batteries used in cars and trucks. The presence of other ions commonly found in tap water will cause a drastic reduction in an automobile’s battery lifespan.

Distilled water is preferable to tap water for use in automotive cooling systems. The minerals and ions typically found in tap water can be corrosive to internal engine components, and can cause a more rapid depletion of the anti-corrosion additives found in most antifreeze formulations.

Using distilled water in steam irons for pressing clothes can help reduce mineral build-up and make the iron last longer. However, many iron manufacturers say that distilled water is no longer necessary in their irons.

Some people use distilled water for household aquariums because it lacks the chemicals found in tap water supplies. It is important to supplement distilled water when using it for fishkeeping; it is too pure to sustain proper chemistry to support an aquarium ecosystem.
Distilled water is also an essential component for use in cigar humidors. Mineral build-up resulting from the use of tap water (including bottled water, such as Dasani or Aquafina) will reduce the effectiveness of the humidor.

Distilled Water was also crucial to the operation of old Boeing 707 airplane engines – it was injected into the engines during take-off, increasing their efficiency by 25%, and during flight on a hot day the use of distilled water was crucial in keeping enough power in the engines to keep the planes in the air.