We will review the principles of water supply, sanitation, and hygiene (washing of hands with soap and water) and their prevalence and health effects. Water supply here refers to the provision of drinking water and water for food preparation, and use in personal hygiene (washing oneself). This water will need to be fresh water. We refer access to fresh drinking water carried to households through pipes from a source from where the water is filtered and made suitable for human consumption and usage as "piped water supply". This is the most desirable access to water. We refer access to "improved" water supply as a situation where even though the water is not carried through pipe from the source to the household, water is nevertheless available in the form of groundwater that is extracted using a handpump, or water that is accessed using a tap installed at a public facility or a fountain installed and maintained by an authority whose water quality is guaranteed. All other facilities or situations where water is obtained at great costs in terms of time and expenses and physical labour is referred to as unfiltered water supply. This water is sourced at its production and is carried to the households by humans in containers, and this water may be contaminated with sewage or other mineral or other forms of contaminants.