This varies from unit to unit. Ritchie fountains range in capacity from 1.2 gallons up to 75 gallons. Ritchie quick refill valves negate the need for a larger trough. Having smaller amounts of water allows the water to turn over quickly and stay fresh. It is also more economical to heat fewer gallons of water. Our largest water capacity trough, the WaterMaster 96, holds 75 gallons and is designed for producers that have low water pressure and need the extra standing water available.