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.
I agree with you on checking your tanks for desiccant powder often. Desiccant powder in your tanks is not good. It will not settle & stay in the tanks. It will always be moving through the coaches air system. It will eventually cause internal leaks in the six packs, check valves, etc. You can rebuild & clean them but the problem will return if you don't eliminate the powder from the tanks. The only way to be rid of the problem is to replace or clean the tanks. Then rebuild & clean the check valves & seals in the six packs. Also blow out & clean the air lines. Believe me I & several others on this forum have 1st hand knowledge.
What did they use to seal the leaks? Something I can get at home depot?