You should always have a pitcher of water available in the fridge for whenever someone needs a glass of water. There are several reasons for this.

First, it is healthy and each person should drink 8 glasses of water a day.

Second, you will save on using disposable plastic water bottles, since you can reuse your own stainless water bottle instead, or simply use a glass.

Third, anyone drinking water won't have to leave the tap running for 5 or so seconds until the water runs cooler.

Fourth, you won't use as many ice cubes for each glass of water, since it will already be cold!