A drip is any abnormal flow of water. Pipe joints drip when they're badly soldered, such as the one at right. Unions drip when they are not tight enough. Drain valves drip when they are not closed tightly. Temperature/pressure relief valves drip when they are doing their job, sometimes. Dripping water heaters may be dying water heaters. The point is: tell us WHAT is dripping; then perhaps we can tell you WHY it's dripping. And what it signifies.

The drip at right, from a faultily soldered joint, was steadily drilling a hole through the painted cover the commercial water heater below it. Left unrepaired, it would eventually destroy the tank from the outside, because a water heater has almost no external rust protection.