9 C.F.R. § 3.10 Watering.
Title 9 - Animals and Animal Products
If potable water is not continually available to the dogs and cats, it must be offered to the dogs and cats as often as necessary to ensure their health and well-being, but not less than twice daily for at least 1 hour each time, unless restricted by the attending veterinarian. Water receptacles must be kept clean and sanitized in accordance with §3.11(b) of this subpart, and before being used to water a different dog or cat or social grouping of dogs or cats.
Title 9: Animals and Animal Products
PART 3—STANDARDS
Subpart A—Specifications for the Humane Handling, Care, Treatment, and Transportation of Dogs and Cats
Animal Health and Husbandry Standards
§ 3.10 Watering.
