A cat that drinks from a running tap but walks past a full bowl is not being difficult. The behaviour has a straightforward explanation rooted in how cats evolved to find water, and it has a practical solution that does not involve leaving your bathroom tap running all day.
The instinct behind it
Cats evolved in dry environments where still water was more likely to be stagnant and unsafe than moving water. A stream, a trickle from a rock, rainfall collecting on leaves, these were the reliable sources. Still water in a pool could carry bacteria, dead insects, or contamination from animals upstream. Moving water carried a signal: it was fresh.
That instinct did not disappear when cats moved indoors. A cat that prefers the tap is responding to the same cue its ancestors used to stay alive. The movement of water, and the sound it makes, registers as fresh and safe in a way that a bowl sitting on the kitchen floor simply does not, no matter how recently you filled it.
There is also a sensory element. Cats have sensitive whiskers, and a deep, narrow bowl forces those whiskers to press against the sides when the cat leans in to drink. This is uncomfortable enough that some cats will avoid the bowl entirely, or drink awkwardly from the edge. A running tap removes the problem, the cat can approach from any angle without its whiskers touching anything.
Why the bowl's location matters too
In the wild, cats do not eat and drink at the same spot. Prey animals contaminate water sources, so a cat's instinct is to keep food and water separate. A water bowl placed next to a food bowl, which is how most owners set things up, can make the water feel wrong even before the cat takes a sip.
The bowl's material matters as well. Plastic holds odours that cats detect even after washing. Some cats will refuse a plastic bowl consistently and drink fine from ceramic or stainless steel. If your cat is selective about the tap but not about which tap, this is worth testing.
When this stops being a preference and becomes a concern
A cat that has always preferred the tap and is otherwise healthy is simply expressing an instinct. A cat that suddenly starts seeking out the tap more urgently, drinking much more than usual, or seems restless and unsatisfied no matter how much water it finds, that is a different picture. Increased thirst is one of the clearest early signs of kidney disease, diabetes, and hyperthyroidism in cats. If the drinking behaviour has changed rather than always been this way, a vet visit is the right next step, not a new water fountain.
Watch for these alongside the change in drinking: more frequent urination, weight loss despite eating normally, a coat that looks dull or unkempt, or a cat that seems less engaged than usual. Any of these alongside a shift in water-seeking behaviour warrants blood and urine tests.
What actually helps
A cat water fountain, a recirculating unit that keeps water moving continuously, solves the problem for most tap-preferring cats. The moving water satisfies the instinct, the filter keeps it fresh, and the cat does not need you to be standing at the sink. Place it away from the food bowl, in a spot the cat already visits. Ceramic or stainless steel units are easier to keep odour-free than plastic ones.
If a fountain is not practical, try placing a wide, shallow bowl in a different room from the food. Wide enough that the whiskers clear the rim. Refresh it twice a day rather than topping it up. Some cats will shift to it without any further intervention once the whisker pressure and the food-proximity problems are removed.
Running the tap on a schedule, morning and evening, can also work as a bridge while you make a longer-term change. It is not ideal because it makes the cat dependent on your routine, but it is better than a cat that is not drinking enough.
A cat that drinks well, whatever its preferred method, is a cat that is less likely to develop urinary crystals and kidney problems over time. Getting the water intake right matters more than which vessel delivers it.