Cymbidiums love water when they are actively growing. Water them 2 to 3 times per week. Keep them dryer during winter months but never let them dry out completely. Water once a week in winter. Tap water is O-K to use but it causes salts to accumulate in the soil.
Cymbidiums are very sensitive to salts in the soil.
Heavy watering helps flush these salts out. I like to use bottled water on my orchids. Bottled water tends to contains fewer impurities. With all that watering, its no surprise to know that Cymbidiums need frequent fertilizing. Choose a good water-soluble orchid fertilizer and apply while watering once or twice per month.