Formula & sources
Usable-water need = measured household mL/day × refill hours/24 + reserve + losses per interval. Use either a combined household measurement or the sum of separate per-cat measurements, not both. Nominal capacity budget = usable-water need + minimum operating water. Available usable capacity = tank capacity minus that minimum. Unknown minimum operating water is not zero.
- Cornell Feline Health Center: HydrationFeline hydration context; enter measured drinking for the budget.
- Grant (2010): Effect of water source on intake and urine concentration in healthy catsResearch on fountains and intake; greater drinking is not guaranteed.
- FDA: Proper Storage of Pet Food & TreatsDaily water-bowl care.
- NIST: SI Appendix B.8 Conversion FactorsUS volume conversions.
Reference values & examples
- Household example
- 450 mL/day
- Refill interval example
- 24 hours
- Reserve example
- 200 mL
- Operating-water example
- 300 mL; device-specific
- Tank example
- 1,000 mL
Three cats drinking a measured 150 mL each per day total 450 mL. With a 24-hour interval, 200 mL reserve, no additional loss and 300 mL minimum operating water, the nominal capacity budget is 950 mL.
Common questions
Can I use separate drinking measurements for each cat?
Yes. Choose either combined household drinking or separate measured daily volumes for each cat, using your selected water unit. A shared bowl cannot identify each cat’s intake; cat count alone cannot determine demand.
Can I confirm a tank is large enough without its minimum operating water?
No. With that minimum unknown, the result covers usable-water need only. Check the device instructions or measure the operating volume with the device off; never run the pump dry.
Does a larger tank mean fewer care checks?
No. Continue daily water and equipment checks even when capacity is ample. A tank budget cannot account for failures, contamination or a tipped reservoir.