New air dryer kit, desiccant leak
I noticed white dust in two front tanks and wet tank. I noticed also the coach would not hold 70 psi when parked for more than 10 days.....so a leak.
Shop found this: five leaks, removed air line and replace two air fittings and four others that were cleaned and resealed. Leaks corrected. The dust was from a leak in the desiccant bag......but it had been replaced with a new bag when rebuilt dryer was installed recently. All was fixed under shop warranty of their work, so that good.
Key reminder.....check tanks regularly, even when.....maybe especially when....new (rebuilt) drier and desiccant installed.