The heyrex torus pet water bowl is ergonomically designed to be perfect for both you and your pet the drinking water flows coolly and freshly into the bowl without electricity or batteries it is stored in the reservoir walls and then flows out through the integrated active carbon filter and so is kept free from dirt dust and bits of food when your pet has a drink the water will filter from the reservoir walls into the centre of the bowl and refill up to the selected level no overflowing