There are two approaches you can take when your cat is drinking from the faucet: 1) make your cat's drinking water more appealing so your cat will more likely drink from there and/or 2) allow your cat to drink from the faucet without creating an inconvenience or wasting water.
There may be several reasons why your cat is drinking water from the faucet instead of a bowl.
Cats instinctively prefer moving water to standing water. Moving water is generally cleaner and safer than standing water. The movement doesn't allow time for things to collect or grow in it.
Better tasteHow often do you clean your cat's drinking bowl? I'm not talking about simply emptying it and refilling it but actually cleaning it before refilling it. Imagine what it would taste like if you reused a drinking glass over and over with only a quick rinse each time.
Better temperatureGenerally the water pipes coming into the house are buried in the ground. This can mean the water is cooler than the air on warm days and cooler than room temperature on cold days. Would you rather have a cool drink or one at room temperature?
Better locationYour cat may simply prefer the location of the faucet when drinking. That could mean a certain location in the house or a certain height above floor level. It could also be somewhere near to you or away from other pets and people.
Whisker fatiqueA cat's whiskers act as sensory tools they use to navigate their environment. The most obvious sense they provide is touch. The whiskers of a cat are sensitive. They can produce overstimulation when they rub against the sides of a small bowl when taking a drink.
Some things to try.If your cat only drinks from the faucet when you're there you can avoid wasting water by being in control of when the water's on and off. But what about when you're not there?
How to avoid wasting waterSome people just leave the faucet turned on with a light stream so their cat can get a drink anytime.
Some smart cats even learn to turn on the faucet themselves when they want a drink. Unfortunately, it's very unlikely that they've learned to turn it off when they're done.
There's a simple solution to avoid wasting water: have an automatic sensor that turns the water on when your cat is near and off when your cat leaves.
Now you could replace your existing faucet with one that automatically turns the water on and off but if you're more budget minded you can buy an attachment designed to do the same thing.
The adapter below simply attaches to any standard faucet as would a water filter and is powered by batteries. You adjust the flow of water that you want. When it senses your cat near it, the water starts flowing just how you set it.
Because this adapter starts the water flow when your cat is near and automatically shuts off the water when your cat leaves, it can preempt or compensate for a cat who has already developed a habit of turning the water on using the handles.
iTouchless EZ Faucet PRO Automatic Sensor Faucet Adapter for Any Sink Faucet
Below is a video of how the iTouchless faucet adapter is installed. Notice the removal of the aerator before the adapter is installed. The aerator is simply unscrewed from the faucet and the adapter is screwed in its place. It's this connection that needs to be standard. If it's not then you'll need a connection adapter (which may come with the product or you can check the home improvement store). You could also just use a different sink that has the appropriate connection.
A different solution provided by Aquapurr is to have a water stream for your cat that is separate from the faucet. It allows your cat to drink faucet water without actually using the faucet itself. That not only frees up the faucet but also doesn't require your cat to get in the sink to use it.
There are six options available for the Aquapurr product.
This is the option seen in the two videos above (minus the decorative wrap and flower in the 1st video).
Two other options let you connect directly to a plumbing supply line (such as the one that connects to the toilet or underneath a sink to the faucet). This allows you to connect the Aquapurr to other plumbing connections besides the faucet.
You can also buy the options above which provide a connection to a faucet and buy just the plumbing tee connector separately at a later date from Aquapurr if you decide you want that kind of connection instead.
The video below shows you how to set up the Aquapurr on the side of a bathtub.
Below is a video showing how to connect the Tee Valve to the water supply for the toilet. Don't worry about having your cat drink toilet water here. This water supply being connected to provides clean water to the toilet tank.
Backup water source
If you do encourage your cat to drink from the faucet you should make sure a backup source of drinking water is available (e.g., water bowl) in case the faucet becomes temporarily unavailable for some reason (e.g., batteries die, power goes out, water gets shut off, bathroom door is closed, etc.).
Faucet connections
The products on this page that connect directly to a faucet are expecting a "standard" connection. It's doubtful you'll find this connection on a tub faucet so we're probably talking about a kitchen or bathroom sink (although you may also have a utility sink located elsewhere that may work).