Potable water is defined as water that is safe for human consumption, meeting established health standards. Non-potable water, by contrast, is water that has not been tested or treated, making it unsafe for drinking or activities involving ingestion, such as washing dishes. While using untreated water for dishwashing is a direct health hazard, it is possible to clean dishes safely if the non-potable water is subjected to a rigorous two-step process of purification and sanitization. This process is necessary because dishes and utensils will directly contact food and the mouth, creating a pathway for contaminants to enter the body.
Why Untreated Water Poses a Danger
Washing dishes with water that has not been disinfected presents health risks due to biological hazards. Untreated water sources often contain pathogens like bacteria, viruses, and parasites. Common examples include E. coli and Salmonella, noroviruses, and the parasitic protozoa Giardia and Cryptosporidium, which can survive on dish surfaces. These microorganisms can easily transfer to the next meal served on the dish, leading to gastrointestinal illnesses and foodborne disease.
A second category of risk involves chemical hazards, which are often invisible and cannot be eliminated by simple disinfection methods. Non-biological contaminants like heavy metals, pesticides, or industrial chemicals from runoff may be present in non-potable sources. Heavy metals, such as lead or arsenic, can cause long-term neurological damage or cancer. While disinfection kills biological agents, it does nothing to remove these chemical contaminants.
Making Non-Potable Water Safe
The process of making non-potable water safe for dishwashing involves ensuring the water is disinfected to eliminate biological risks. Before disinfection, the water should be pre-treated to remove large particulates that can interfere with the efficacy of purification. This is accomplished by allowing the water to stand until suspended sediment settles, or by filtering it through a clean cloth or coffee filter to strain out visible debris.
One reliable method for killing waterborne biological pathogens is to bring the water to a rolling boil for at least one full minute. At higher elevations, specifically above 6,500 feet, the water must be boiled for three minutes. Boiling is the most effective way to destroy parasites, including Giardia and Cryptosporidium, which are resistant to chemical treatments.
If boiling is not possible, chemical disinfection using unscented household bleach is a viable alternative. For water that appears clear, the recommended ratio is 8 drops (or 1/8 teaspoon) of bleach for every gallon of water. If the water is cloudy or murky, the dosage should be doubled to 16 drops (or 1/4 teaspoon) per gallon.
After the bleach is added, the mixture must be stirred thoroughly and allowed to stand for a minimum of 30 minutes to allow the chlorine to work. The water should have a slight, detectable chlorine odor after this time; if no odor is present, the dosage should be repeated, and the water should stand for another 15 minutes.
The Proper Procedure for Washing Dishes
The first step in using the treated water is to conserve this prepared resource by removing as much food waste as possible from the dishes. All plates, bowls, and utensils should be scraped or wiped clean of residual food before they are introduced to the wash water. This action helps keep the treated wash water cleaner for a longer period and prevents organic matter from neutralizing the soap’s effectiveness.
The actual washing process should take place in a designated wash sink or container filled with the treated water and dish soap. The goal of this stage is the mechanical removal of grease and food particles through thorough scrubbing. It is most efficient to start with the least soiled items, such as glassware and cutlery, and save heavily soiled pots and pans for last, as this keeps the wash water usable for longer.
The cleaned dishes must then be moved to a separate container for the final sanitization step. Sanitizing is necessary to kill any residual germs that may have survived the washing process or were not eliminated during the water treatment. One method is to use a high-heat soak, submerging the dishes completely in water that is at least 170°F for 30 seconds.
If high-heat water is unavailable, a chemical sanitizing dip is required, created by mixing a weak bleach solution in a separate rinse container. A common ratio for this sanitizing dip is one tablespoon of unscented chlorine bleach mixed into one gallon of clean, treated water. The scrubbed and rinsed dishes must be fully submerged in this solution for at least one minute. The final step is allowing the dishes to completely air-dry on a rack without being wiped with a towel, as cloth towels can easily reintroduce bacteria and other contaminants.