I have been chasing a water leak in my Class A motorhome for 3 weeks . I had a small leak only when it would rain heavy . The area under bathroom vanity would get wet between the shower base and vanity. The water was entering the motorhome through the vent pipe chase area near Maxx air vent . I removed all sealant around roof vent and vent cap and resealed . The next time it rained heavy, still getting wet. The way I found it was isolated to this area was , when it was below freezing I could walk on the roof and you could hear the ice underneath the aluminum just in that area. The next thing I resealed was the skylight over the shower . That's when I found the real problem! The aluminum between the vent and the skylight had 9-10 pin holes they were very small and very hard to see. They looked like discolorations in the aluminum, until you touch them with a pick and they were holes. I just wanted to let people know about this, to hopefully save you time in future .