The first thing to know when wondering if your horse is drinking too much water is how much your horse actually drinks on average per day. If you don’t know your horse’s normal water consumption, it is difficult to know abnormal. Normal water consumption in a 1000-lb horse is about 5-10 gallons per day depending on the weather, although some horses on pasture may normally only drink 3-4 gallons and some horses in hot environments or mares nursing foals may drink 15 gallons per day. So it is important to know how much your horse drinks per day so you can know if that amount changes.
Polydipsia is the term for increased water consumption, which in horses is defined as consuming more than 50 milliliters per pound of horse. For a 1000-pound horse, this is about 13 gallons per day, so you see there is some overlap. However, this average number of 13 gallons is for a normal nonpregnant and non-exercising horse with a normal outside temperature. Another thing you may notice if your stalled horse is drinking too much water is an excessive amount of urine in the stall; if you see this, it is important to consult your vet. The two most common diseases in horses that cause increased water consumption are chronic kidney failure and Cushing’s disease. There are many other potential causes but if your horse is drinking excessive water, it is a good idea to have your vet perform an exam and check some blood work. If kidney disease is involved, a change in diet may be helpful and if Cushing’s disease is diagnosed, a medication can help prevent some of the conditions caused by the disease, such as laminitis and founder.