A common hazard of household water is contamination by potentially harmful bacteria and other micro-organisms. Short term gastrointestinal disorders and illnesses such as gastro‑enteritis, giardiasis, typhoid, dysentery, cholera, and hepatitis have been linked to water contaminated by microorganisms.

When preparing for a disaster, it is important to provide for an adequate supply of water for drinking and cooking. In natural disasters, such as floods, hurricanes, or earthquakes, the municipal water supply is likely to be disrupted. Ice storms and other emergencies can cause a loss of electrical power, leaving well pumps unable to function.

Concerns about personal and family health may lead you to question the safety of the water used in your household.

Many areas have water containing impurities from natural or artificial sources. These impurities may cause health problems, damage equipment or plumbing, or make the water undesirable due to taste, odor, appearance or staining.

Hydrogen sulfide gas is a nuisance that is not usually a health risk at concentrations normally found in household water. Water containing hydrogen sulfide, commonly called sulfur water, has a distinctive “rotten egg” odor, which may be especially noticeable when running hot water. Such water can discolor coffee, tea and other beverages, and alter the appearance and taste of cooked foods.

People are exposed to lead from a variety of sources. In Virginia there are negligible amounts of lead in surface water and groundwater, but the water in household plumbing systems can contain high levels of lead. Because lead is a serious health hazard, it is very important to reduce lead contamination of drinking water.

Nitrate (NO3) is the primary source of nitrogen (N) for plants; they cannot live without this nutrient. Nitrate contamination
of a water supply occurs when there is more nitrate in the soil than plants can use and when water can move easily through the soil and underlying rock.

Foul taste, smell, or color of your household water may prompt you to investigate water treatment equipment. The publicity about water pollution problems may cause you to question the safety of your water supply. Or mineral scale buildup may cause you to invest in early replacement of plumbing fixtures and water-using appliances.

Iron and manganese are metallic elements that are found in the earth's crust. These elements usually do not present a health hazard when they are present in the household water supply; however, they can cause nuisance problems, such as staining and objectionable taste.

Until recently, the point‑of‑use water treatment industry focused on improving the aesthetic quality of drinking water. The industry has lately been thrust into the forefront of treatment of contaminated drinking waters that pose a serious health hazard. The response has been a plethora of companies and products promising to render the consumer’s drinking water safe and contaminant free.