Water pump check valve - fresh tank overflowing

It's certainly something that Shouldn't Happen™, and if it's under warranty I would certainly add it to the list for the dealer to take care of.

If it happens again out of warranty, all the advice here already is valid. I exclusively use my water tank; filling the tank every couple of days is WAY worth avoiding overpressure, backpressure, hose trouble, etc. for me.