water-drinker
/ˈwɔːtə ˌdrɪŋkə/noun
1A person who drinks water, especially in preference to wine or other alcoholic drinks; (sometimes) specifically a teetotaller.
2A person who drinks the waters at a spa or spring. Now historical.
Origin
Late Middle English; earliest use found in Promptorium Parvulorum. From water + drinker.