A cat drinking a lot of water can be a symptom of illness, since our feline friends do not like it very much. So pay attention to the amount of liquid it drinks to protect its health.
Cats usually drink between 80 and 100 ml of water for every kg from its body if it eats dry food and only 50 ml if it eats wet food. If is drinks more than this quantities, it is considered to be drinking excessively. When they feel the need to drink more water than usual (polydipsia) it is because their body is losing fluid and they feel dehydrated. This intake is usually accompanied by an increased need to urinate (polyuria).
These two symptoms usually appear when there are kidney diseases, although they can also appear in cats with diabetes or hyperthyroidism. Sometimes the reason may not be linked to a health problem and may be due to the increase of exercise or heater weather. Both can cause the animal to drink more.
You will also have to pay attention to other aspects such as the water fountain and if it empties faster than usual, if pet demands your attention asking for more water or if it visits more often places where water is within reach of cat, such as the bathroom.
It is convenient you try to make your pet pee in its litter box. It is the only way to check how often you have to change cat litter and if the frequency of the change is increasing.
If your cat drinks a lot of water, never deny it. What you should do is go to the vet to find the reason, but you must allow the cat to drink everything it demands, because that means that it needs it.