Ventilation of a water reservoir of a drinking fountain for a pet

A pet fountain comprising:

• a water reservoir comprised of a water discharging end;
• and
• a spout connected with said water discharging end water reservoir;
• wherein said water reservoir is further comprised of a ventilation end which is comprised of a through hole in communication with an interior of said water reservoir, and an elastic ventilation block dimensioned to fit airtightly into said through hole, said elastic ventilation block being comprised of a fitting portion and a projection extending from said fitting portion, said fitting portion comprised of a ventilation hole, said projection comprised of a slit in communication with said ventilation hole of said fitting portion whereby elastic ventilation block is fitted airtightly and removably into said through hole of said ventilation end of said water reservoir such that said fitting portion is received airtightly and removably in said through hole, such that said projection is extended into the interior of said water reservoir, such that the interior of said water reservoir, and such that the interior of said water reservoir is in communication with atmospheric air via said slit of said projection and said ventilation hole of said fitting portion.