Distillation is a process in which water is boiled, and the resulting steam is collected and condensed to produce purified water free of impurities. Distillation treatment is effective against removing heavy metals, dissolved solids, some bacteria, viruses, some organic chemicals, and inorganic materials such as nitrate, sodium, fluoride, and sulfate. Distillation treatment is not effective at removing most volatile organic compounds and some bacteria.
How Distillation Works
The distillation unit heats tap water to its boiling point, which kills most bacteria and viruses. As the water boils, it produces steam that rises, leaving impurities behind. The steam then passes through condensing coils, where it cools and returns to liquid form. The resulting distilled water is collected in a storage tank.
With minimal additional treatment, distillation produces nearly pure water. Because most minerals and salts are removed, distilled water is almost entirely mineral-free, which can result in a “flat” taste.
Distillation typically removes up to 99.9% of dissolved substances. However, certain volatile and semi-volatile organic compounds may not be effectively removed through this process. When the boiling points of these compounds are close to that of water, separation by distillation becomes difficult. If such contaminants are present in the water, they should be removed prior to distillation. Otherwise, they may vaporize with the steam and condense back into the purified water, leading to recontamination.
Types of Units
Distillers vary from small, round units that distill less than one quart of water per hour to larger, rectangular carts, which distill about one-half gallon of water per hour. Because distillation units produce a small amount of treated water, they are typically installed as point-of-use units at the faucet and are not used to treat all the water entering the house. Before purchasing a system, verify that the treatment system you are purchasing has been tested and certified by a third-party to ensure manufacturer’s claims.
Distillers can be filled with water either manually or by a connection to a water supply line. Permanently installed water distillers should have a drain opening to remove contaminated water. Faucets facilitate the draining of countertop units.
Storage containers store the distilled water. Glass jars are attached to the unit on some models. Other units have a metal tank into which the condensed steam drips. A third type of container is a plastic bottle. The volume a container can hold can vary from 1 to 15 gallons of water.
Automatic features on units include reset switches and timers that make automatic operation possible on some installed models. These features might be desirable when distilled water is used continuously.
Regardless of the quality of the equipment purchased, it will not perform satisfactorily unless maintained in accordance with the manufacturer’s recommendations for maintenance, cleaning, and part replacement. Keep a logbook to record equipment maintenance and repairs.
The boiling chamber of a distillation system accumulates minerals over time and needs to be cleaned periodically. Cleaning frequency will depend on the level of minerals in the water and the amount of water being used. In some cases, the mineral build-up can be dissolved by diluting acid cleaners in a heated condition. Always follow the manufacturer’s cleaning recommendations
Other Considerations
Ensure the system is installed and operated according to the manufacturer’s instructions. After installation, retest both the raw water (prior to treatment) and the treated water at a state certified laboratory. Compare the two results to ensure the treatment system is working properly and is removing the contaminants. The quality of both the raw and treated water should be tested annually or more frequently (quarterly or semi-annually) if high levels of contaminants are present in the raw water. Frequent testing will also help determine how well the treatment system works and whether maintenance or replacement of components may be necessary.
Questions to Ask Before You Buy
Before purchasing a water treatment device, have your water tested at a state certified laboratory to determine the contaminants present. This will help you determine if distillation is an effective treatment method for your situation.
Consumers should inquire about the following before purchasing a distillation system:
- Confirm that distillation is the effective treatment method and will remove the contaminants present in your water.
- The type of distillation unit that best suits your water quality needs.
- Has the treatment system been tested and certified by a third party to ensure that it meets the manufacturer’s claims?
- Does the storage tank hold enough treated water for daily use?
- How often will the distillers need to be cleaned?
- Are there any special installation requirements that may add to the equipment cost, for instance, changes to your household plumbing?
Please refer to Questions to Ask When Purchasing Home Water Treatment Equipment for more information.
Product Certification
NSF International is a non-profit organization that sets performance standards for water treatment devices and chemicals. Because companies can make unsubstantiated statements regarding product effectiveness, the consumer must evaluate test results of the device to determine if claims are realistic. Products that have been tested or evaluated by NSF and meet their minimum requirements are entitled to display the NSF listing mark on the products or in advertising literature for products. Manufacturers and models that meet NSF’s standard are included in a list published twice a year. Contact NSF International by phone at 800-673-6275 or search for certified products on NSF's online database.