Open valleys are best.
If you have a tile roof in the Northern California location, chances are good that you have a Closed Valley.
And Open Valley in your tile roof will help the roof clear it's self when it rains.
Other areas in California, like the central coast, have Open Valleys built as a normal method of installation practice.
Call today and let Andy put you on Galaxy Roofing's calendar for a good start date to a better fix