I have thought about a spare tank for my 5th wheel but one thing concerns me. There are some bridges and tunnels that will not allow you to carry a spare tank. The Chesapeake bay bridge tunnel is one route you will not be allowed access to
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COMPRESSED GAS REGULATIONS
For Non-Commercial Vehicles
Maximum capacity: (a) Not more than two non-permanently mounted containers having maximum individual capacity of 105 pounds water capacity or 45 pounds LP-Gas each, or one container having maximum capacity of 60 pounds LP-Gas, or (b) not more than two permanently mounted containers having maximum total capacity of 200 gallons water capacity LP-Gas when used as a motor fuel. Tanks must meet the approved standards of the Department of Transportation and are subject to inspection at toll plaza. They must be properly secured and valves closed while crossing the facility.
For a printable version of the Chesapeake Bay Bridge-Tunnel's current Toll Schedule, click here. (Adobe Reader Required)