Experiment 1 found that rats regulated the number of drinks per session during schedule-induced polydipsia, rather than volume intake when water was obtained from different sized water dipper cups. However, when water availability was manipulated during polydipsia sessions by changing the aperture size of the water bottle tube (Experiment 2), the rats regulated total water-intake volume per session. Experiment 3 demonstrated that this volume regulation was more precise during schedule-induced drinking than during water deprivation induced drinking. Also, it was shown that the different sized apertures were effective in manipulating the rates of water availability and ingestion. These experiments demonstrated that volume regulation during schedule-induced polydipsia occurs only when water is freely available via drinking tubes.