Hi, I have a fairly large moss garden that is never watered. Rain only. It's surived several major yearly droughts just fine. Too much water in warm weather can be deadly for moss (fungus infections). Conseqently, I hate a wet summer. Moss is safer going dormant in the summer. I transplant in cold rainy weather and rarely loss any moss. Winter before a snow is ideal. If you do put in a system, don't use it in warm weather. Pulling up dead moss & treating with dyconil is not fun. You might get some outstanding growth used at 55 degrees F or below. After the droughts, the last 2 wet fall/winters have been exciting in my moss garden.
Best regards, jjane