Well I got a 100 gal semi tank. I made a cradle for it to sit in the bed, since it is only for roadtrips. I'm also putting a topper on the truck. The tank has four main holes. 2 on top, 2 on bottom. When I got it, the top 2 were feed and return, and the bottom 2 were plugged. I'm plugging the top 2, one on the bottom and I put in a 1/2 NPT male to male nipple, followed by 1/2 valve, then to a 1/2 NPT to 3/8 hose barb. With the cradle I made the nipple is about 1/4 above the bed. I'm going to drill a hole then gravity feed it into the main tank. Question is,the tank also has a hose on top that only allows air in. Can I leave that open inside the topper? Or run it under the trucka nd put a small filter on it. Also how do these tanks vent air out? Also the main fuel tank cap only vents air in also right? so if the semi tank is filled, don't open the truck's tank. Would there be any problem with this, worried about the truck's retrun fuel system pressurizing the main tank if it will remain full dur to the semi tank. I can't have the tank vent inside the topper, since our dog will be back there this one time, for the move. Thanks. Just want to do this right the first time. plus 100gal would make a big mess if it makes the main tank overfill.

 

That short little hose is the vent. Extend it to vent outside of the topper. I would install a fuel filter on that tank also.

Will probably want to istall an electric valve, unless you want to get in and out. Should leave the valve open.

Plus, I don't think the DOT likes the gravity fed setup to much.

 

Any idea os where to get a little electric valve? I'll search for one now. Hoping DOT doesn't notice the setup with the topper on.

 

Use a motorized fuel tank selector valve made by Pollak. Kit #42-300. comes with valve, switch and plug connector. You can plumb in the fuel supply and return and a fuel guage sender. Works great. The DOT does not like bottom feed tanks, but they mainly watch commercial and leave us poor people alone.
This kit should sell for around $60. Good luck

 

Cool, Thanks, one more question, what about a filter? any special style? Just read a post about someone getting a bad tank of fuel. So I think a filter is extra insurance, especially if I only fill the aux tank on the road, that way the fuel is filtered twice before hitting the VP. Thanks again

 

You may have a big mess on your hands if you gravity feed a 100 gal tank. The transfer kit sounds a lot better if it will transfer until your main tank is full and then shut off. If you went with the gravity feed, your main tank will overflow fuel all over and you will be in deep doo-doo. DOT doesn't like gravity feed because if you got a hole in one 100 gallon tank and both were filled you would end up with a 200 gallon spill. The aux. in bed tanks, normally, are set to start transfering fuel at about 1/2 full in main tank and stop when the main is full.