No it's the water tank When they molded it you can see where it was really thin. At first I thought they might have nicked it with a saw or grinder when they installed the cheater vent for the shower drain. After I removed it you could clearly see where it was paper thin. Just disappointed that someone would install it like that.Held up for 8 years but filling with a 5/8 hose and having a 1/2 overflow I'm sure the pressure finally blew the thin part out.After a couple of 5th wheels and diesel pusher doing maintenance on them you really see how these rvs are put together.