Realistically, the actual concept
of "fountain" is very rarely signed. Most often we simply ask "WATER,
WHERE?" Or "I/me THIRSTY, WATER WHERE?" And the other person tells us where.
But if you do need to express the concept of a "drinking fountain" you sign
WATER and then mime the use of a fountain.
DRINKING-FOUNTAIN:



Notes:
Years back most fountains had knobs. Then after
the Americans With Disabilities Act was passed fountains started
being built with surfaces that you press on (thus making the
fountain easier to use if your hands can't grip or turn knobs).
See:
THIRSTY
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American Sign Language (ASL) online at American Sign Language University ™
ASL resources by Lifeprint.com © Dr. William Vicars