This depends on their diet, and the temperature. Like us, if it’s a warm summer’s day then we lose a lot of moisture and get pretty thirsty, so we’ll need more to drink. Also, if we eat a lot of dry food like crackers then we’ll need to top up on moisture.
How much your guinea pigs need to drink also depends on their level of physical activity, their size, and whether or not they’re pregnant. This all sounds pretty complicated but there’s nothing to worry about, because as long as you keep their water bottle full and clean then your guinea pigs will always have enough to drink. Bear in mind though, that if it’s summer no amount of water will make up for shade – whether your guinea pigs are outside or inside they’ll need a cool, shaded place not above 24 degrees celsius. For this reason, we strongly advise against keeping guinea pigs in conservatories because these are areas that tend to get very hot very quickly.