The steam then cools and condenses to form purified water. The boiling process also kills microorganisms such as bacteria and some viruses. The effectiveness of distillation in removing organic compounds varies, depending on such chemical characteristics of the organic compound as solubility and boiling point. If these harmful compounds are not removed prior to condensation, they will re-contaminate the purified product. Distillation units are usually installed as point of use systems.
Stills vary in size, depending on the amount of purified water they produce.
The production rate varies from 3 to 11 gallons per day. Home stills can be located on the counter or floor, or attached to the wall. Models can be fully or partially automated, or manual. Some stills have columns or volatile gas vents to eliminate organic chemicals with boiling points lower than water, thus ensuring uncontaminated water. Unevaporated pollutants remaining in the boiling chamber need to be regularly flushed to the septic or sewer system.