The fresh water tanks on our 2015 28BHBE equalize through a 1.25" line at the bottom and 2 .5" lines at the top. The tanks also can float around a bit in their mount system. I stabilized my tanks with high density foam so they wont shift. Also, if you put shutoff valves on the overflow lines, and open them when filling, but close them when travelling, you retain all the water you put in your tanks. ( i lost 1/3rd of my capacity in 200 miles).
'07 Chevrolet Silverado 3500HD XC LB SRW 4X2.
Powerstop Brakes on all corners.
'15 JayFlight 28BHBE Elite Fibreglass
'07 Northern Lite 10-2RR Camper.