Join Date: May 2007
Location: Glen Cove, NY
Thanked 76 Times in 70 Posts
Rep Power: 9
If you tee into the vent line I would be concerned about fuel backing up and spilling out into the water. With two tanks it is essential that when you shift tanks, you shift both supply and returns. Otherwise you are pulling fuel from one and returning to the other. One will run dry and the other will overflow.
Strange that the second tank doesn't have a return connection. Is it really a diesel tank or was it a gas tank?