Distillers are commonly used for removing nitrate, bacteria, sodium, hardness, dissolved solids, most organic compounds, heavy metals and radionucleides from water, and ultimately, remove about 99.5 percent of the impurities from the source water.

Distillers can allow 0.3 to 0.5 percent of water impurities to exist in the storage container after distilling.

Some volatile organic contaminants (VOCs), certain pesticides and volatile solvents, boil at temperatures very close to water (207-218 degrees Fahrenheit). These types of contaminants will not be substantially reduced in concentration by distillation.

Properly equipped distillers can reduce VOC concentrations effectively. Although bacteria are removed by distillation, they may recolonize on the cooling coils during inactive periods.

Distillers use heat to boil water into steam that is condensed back into water and collected in a purer form. When water boils, it leaves impurities behind in the boiling chamber.

The rising steam passes into a cooling section and condenses back into a liquid. The condensed liquid (water) then flows into a storage container.

Distillers remove almost all of the impurities from water supplies. As water is heated, the impurities in the boiling chamber increase in concentration. The water left behind in the boiling chamber is discarded and the process is started over.

Distillers are commonly made of stainless steel, aluminum and plastic materials. There are two types of distillers:

Water is poured directly into the boiling chamber. The unit is turned on and the water is heated to boiling. When all the water in the boiling chamber is evaporated, the unit shuts off.

Distilled water is removed from the storage container for household use.

Batch units can range from one-gallon countertop units to 10-gallon floor units. Batch distillers produce from three to 10 gallons of distilled water per day. The smallest distillers are about the same size as a coffee maker.

Continuous flow or automatic units are connected to the water supply line. A float valve connected to the water supply maintains the water level in the boiling chamber.

As distilled water is removed from the storage tank, the unit turns itself on and starts producing more distilled water.

A discharge line periodically removes the concentrated impurities from the boiling chamber. Distilled water is either stored in a container or is piped to the use area.

Additional storage containers, transfer pumps and special kitchen taps can be installed adjacent to a distiller. Increased storage capacity will only be advantageous for continuous flow units. For example, you can install a kitchen tap and an under-the-sink reserve tank that has a level switch to turn on a small transfer pump.

This pump transfers water from the distiller to a storage container located under the sink. When the under-the-sink reserve tank empties it turns on the transfer pump to refill the reserve tank.

When the distiller's storage tank empties, it turns itself on and fills the storage containers.

Distillers can remove VOCs by three methods:

1. Gas vents;
2. Activated carbon filters (ACF); and
3. Fractional columns.

Distillers that use a combination of VOC removal methods are more efficient than one single method.

Gas vents — Small holes drilled into the passage leading to the cooling coils. Gas vents allow VOCs to escape the distiller before they enter the cooling section coils. These holes (one or two) are usually from .045 inches to .065 inches in diameter.

Activated carbon filters — Trap VOCs. The ACF units are normally located at the end of the cooling coils and remove the VOCs prior to entering the distilled water storage container.

ACFs can also be placed in the water supply line to reduce VOCs entering a distiller.

Fractional column distillers — Use differential cooling to remove VOCs. VOCs are removed when they condense in a different section of the fractional column than where water does.

Removal of VOCs in distillers without gas vents, fractional columns or ACFs can also be accomplished with some success by discarding the first pint (1/2 liter) of distilled water in the storage container. n

Russell Derickson is the Extension Associate in Water and Natural Resources, North Dakota State University Extension Service, Fargo, ND. Fred Bergsrud is the Water Quality Coordinator, University of Minnesota Extension Service, St. Paul, MN. Bruce Seelig is the Water Quality Specialist, South Dakota State University Extension Service, Brookings, SD.

FS-5Drinking Water: Treatment Guidelines. University of Maryland Extension

9.729Drinking Water Treatment Devices: Distillers. Colorado State University Extension

HE-430HouseHold Water Treatment. North Dakota State University Extension

MWPS-14 Private Water Systems. Midwest Plan Service

Water Treatment Handbook. Rodale Testing