All Auxilliary Fuel Tank Users-Sight Glass or Not?

[PUG]

I am building an auxillairy fuel tank that goes under my toolbox. I am trying to keep it as simple and cheap as I can. It will have gravity flow into a RDS kit on the fuel fill line, vented, etc.

Instead of a fuel guage, I am considering putting in two bungs into the side of the tank with fittings and a clear tube that I can see from the bed. The clear tube would show the level of the fuel in the tank. I would also have a fuel shut off valve in the same area.

Other than the inconvenience of not seeing the level from inside the tank, are there any do's or don'ts? Or better ideas?

 

[lwmcguir]

How about using a float type gauge that you could see from the side. Most sight gauges with lines get broken eventually.

 

[hoefler]

You can buy a univerasl gauge kit for about $30. Sight glasses are not DOT Approved.

 

[caissiel]

I build my own tank and at the time I build it smaller then the truck tank. Now I have a long wheel base with a larger tank. So at 1/4 tank no way can I overfill my truck tank.

I have the tank vented thru the bottom tank, using the truck cap do all the venting and releiving. The truck cap is half way up the top tank so I will never overfill the bottom tank when I dump. I use the truck gauge to tell me when to shut off the dump tank.

My setup includes a solenoid valve with isolation valve and a bypass valve if the solenoid valve fails or the filter plugs. In the last 3 years I have never had to change the 10 Micron filter.

I had to tie the vent of the top tank to the bottom tank so that whendumping the air from the truck tank vents to the top tank while the fuel fills the truck tank.
My friend had a setup with a vented tank and the top drained real slow because the venting of the bottom tank is thru the cap instead. And mostly a requirement of a pump is then required and then it needs certification.