Emerging evidence suggests that widespread failure in coordination and collaboration between the health and WaSH sectors contributes to the substantive disease burden associated with inadequate water, sanitation and hygiene (WaSH). This results in missed opportunities at every level starting with access to water and sanitation and adequate hygiene practices in primary health facilities. This paper describes the application of an established health system functions framework to the WaSH sector and summarizes examples of successful health system action including the roles played by diverse health professionals.