'02 9400 fuel drains to low side tank

Greetings friends. When I sit on slope, the fuel on my 9400 with dual 150 tanks, drains to the low side. I have to keep about 100 gallons minimum to keep in above the pick up tube on the high side. Is this normal for international trucks? My old Volvo had a splitter valve to prevent this from happening. I know I could keep the tanks full, be some loads there is a weight concern carrying 300 gallons. I know right now I have at least 100 gallons, and after sitting for about 4 hours on an incline in a rest area, it drew air on the high side and lost its prime. Now i'm waiting for service truck to get me started. Are international trucks equipped with this valve? If not can one be added?

 

Thanks for the reply. I noticed there is a "T" right behind the engine, attached to a bell housing bolt. Would this be the valve you speak of? Is it just a regular T, or does it have check balls in it? I don't quite understand what you mean about the clear line though.

While I was waiting for service truck, a nice lady offered help. She went to get me a gallon of fuel to fill the Davco filter. I used the primer pump to get it to run enough to get the empty tank on the low side. I put the red line in the tank with the most fuel in it, but it didn't move it to the low tank. But I heard air escaping from somewhere up around the engine. I would sure apprecIate any more help and suggestions you can give.
By the way, I filled it up when I got to fuel stop. Took 187 gallons. So I know there was at least 100 gallons in there. Thanks.