Fairfax Water’s Water Quality Laboratory, a state certified laboratory, performs or manages the testing required by State and Federal regulations. In addition to regulatory testing many other analyses are performed to monitor the water quality of the Authority’s raw sources, water within the treatment process, as well as within the distribution system. Water undergoing the treatment process is continuously monitored for pH, turbidity, coagulation efficiency, and disinfectant residuals through technically advanced on-line monitoring systems. Other testing, such as chlorine, pH, and temperature, is performed at the sample location site with portable instrumentation. The majority of the regulatory and water quality monitoring testing performed, which include Organic, Inorganic, Metals, and Bacteriological testing, are conducted at Fairfax Water’s laboratory using sophisticated instrumentation. Results for much of this testing are posted on Fairfax Water's website in its Annual Water Quality Report.

Fairfax Water uses chlorine for disinfection purposes, which can be harmful to fish if not dechlorinated prior to placing fish in it. Fairfax Water utilizes two types of chlorine, free chlorine and chloramines (chlorine and ammonia mixture). Chloramines are normally used July - March, and free chlorine is generally used April - June. Free chlorine and chloramine dechlorination is performed differently. Chemical additives with directions for dechlorinating either free chlorine or chloramine from water for use in fish tanks or ponds are available at pet/fish supply stores.

The white residues are minerals that are found in the water such as calcium. Overtime and repeated water use there may be a build-up of the minerals on any item the water comes in contact with. There are commercial products that can be purchased to rid the surface of mineral build-up.

Ice cubes freeze from the outside in. Ice is formed from pure water (hydrogen and oxygen) therefore the minerals such as calcium and magnesium normally found in the water sometimes end up as visible particulates in the core of the ice cube. The white particles are not toxic.

Hot water generally comes from a hot water heater that may contain impurities that should not be ingested. Some of these impurities might be metals from household plumbing that are concentrated in the heating process. Additionally, these impurities from the household plumbing dissolve more rapidly in hot water than cold water causing the amount of impurities to be higher in hot water.