It is important to water a lead acid battery because the water is used as a medium for the flow of ions between the battery's positive and negative plates, which is essential for the battery's proper function. The water in the battery's electrolyte also helps to regulate its temperature and prevent it from overheating.

Over time, water in a lead acid battery can evaporate due to the heat generated during charging or use. If the water level falls too low, the exposed lead plates can become damaged, which can lead to a reduction in the battery's capacity and overall performance.

Therefore, it is important to regularly check the water level in your lead acid battery and add distilled water as needed to ensure that the battery remains properly hydrated and functioning at its best.