Transfer tanks

[terrible ted]

Who know the law on them. I want to fill my100 gallon tank with avgas for my boat. I like to put the tank in a trailer instead of my truck. been looking online not a true clear answer.

 

[Slidin Gator]

The tank needs to be DOT rated for gasoline. A lot are rated for diesel but not gas. Legally it needs the gas rating to run down the highway other than inside your boat (where Coast Guard rules apply).

This assumes a NON enclosed trailer. I don't know the law if the trailer is enclosed, but I imagine you at least need to vent it outside like a marine tank.

 

[JLP3314]

Slidin Gator,

I always wondered why DOT did that. Is there much differences in the construction or venting on the two different tanks?

 

[Slidin Gator]

Slidin Gator,

I always wondered why DOT did that. Is there much differences in the construction or venting on the two different tanks?

To my knowledge, the primary issue comes down to fuel feed, you can gravity feed from the bottom of a diesel tank but for gasoline you have to draw from the top. Also note that there is a full set of tests that have to be done to achieve DOT rating and I believe the gasoline rating is more stringent, or at least has to be repeated (separate for gas and diesel). So making them dual rated is more expensive and therefore the diesel folks get more options.

My son worked at a test lab and they were running a DOT qualification drop test on a new 95-gallon steel diesel tank design. The company sent them 2x units, they filled the tank with water, lifted it with a crane and dropped it on a corner onto concrete. It passed the first time (hit on corner and didn't leak) so they ended up with an extra.

In other news, I now have a nice 95-gallon steel fuel tank on my diesel generator

RDS is a big supplier of auxiliary fuel tanks and I think they explain it well on their website.
Contact RDS

Auxiliary tanks connect to your vehicle’s fuel tank. Diesel fuel can “gravity feed” from the bottom of your RDS tank.

An optional Diesel Install Kit contains the necessary items to economically and easily connect your RDS tank to your OEM fuel tank.

Gasoline auxiliary fueling is allowed, if siphoned from the top of the tank by using an electric fuel pump

Transfer tanks fuel other equipment or vehicles. These tanks have a structurally reinforced 2” FTP coupling for installing a hand or electric fuel pump.

Most RDS transfer tanks also provide auxiliary fueling.

From my findings most "Transfer" type tanks are dual rated diesel or gasoline etc. It is the "Auxiliary" tanks that many/most are just diesel rated and I believe this is because the market is mostly diesel, so they don't bother putting the top mounted fuel draw connection. I talked to RDS a while back about a fuel tank for my swamp buggy. As it turns out, there are no laws regulating buggy fuel tanks (imagine that!), so I went with a "Diesel" rated tank with a bottom connection for gravity feed to the filter and fuel pump keeps everything happy. Do note that I added a shut off valve at the tank in case of a leak in the fuel system.