Tanker Test Study Guide for the CDL

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General Information

The Commercial Driver’s License (CDL) Tanker test is used to determine if potential drivers are able to safely operate a tanker (a vehicle designed to transport liquid or gas). Safety is pivotal when determining if a driver should be working on the road. Tankers are large and exceedingly heavy. Tankers handle quite differently than other commercial vehicles and require vehicle-specific maintenance, inspection, and safety procedures.

Do You Need A Tankers Endorsement?

You need a Tankers Endorsement if you haul a liquid or a liquid gas:

  • where the capacity of any one tank is more than 119 gallons or
  • where the total aggregate capacity of all the vehicle’s tanks is 1,000 gallons or more

It doesn’t matter if the tanks contain HazMat. It doesn’t matter if the tanks are permanently or temporarily attached to the vehicle. If the tank(s) are above either (or both) limits, you need a Tankers Endorsement.

Flatbedding Exception

If the tank is empty, not designed for transportation, and temporarily attached to a flatbed trailer, the trailer is not a tanker.

Commercial Learner’s Permit (CLP) Exception

If you have a CLP with a tank endorsement, you can operate a tank vehicle if it is empty. If the empty tank had previously contained HazMat, the tank must have been purged.


Tank vehicles are more complicated than other types of vehicles. The very nature of transporting products in tanks requires specialized piping, valves, and handling systems. Check owner’s manuals before attempting to inspect or operate tank systems.

Check For Leaks

All inspection of commercial vehicles should include a check for leaks. The obvious place to look for signs of leaking is on the ground, under the vehicle. Also check the frame and the under-frame equipment for signs of leaking material.

Also check:

  • tank body (shell) free of dents and leaks
  • intake/discharge ports and cut-off valves
  • valves (not leaking and in correct position)
  • pipes (especially at joints and elbows)
  • hoses in good condition and stored correctly
  • manhole covers closed and latched (and/or sealed)
  • vents are clear, not leaking, and functioning normally
  • all covers and ports have gaskets and close normally
  • tires in good condition (check for leaking material on tires and in “tire spray”)

Special Purpose Equipment

Some tankers are equipped with specialized operating, safety, and emergency equipment:

  • vapor recovery kits
  • grounding/bonding cables
  • emergency shutoff equipment
  • built-in fire extinguishers
  • automatic fire suppression system

Fire and Safety Equipment

Depending on what is carried in the tank, you might need additional equipment. This includes Personal Protective Equipment (PPE), special equipment for the tanks, or specialized safety equipment. Find out what is needed, and be certain everything works.

Unsafe Equipment

Do not use tanks that are leaking. You can be fined and/or shut down. You might be responsible for cleaning any spills. Never drive a vehicle with open valves or manhole covers.

High Center of Gravity and Rollover Risk

Truck Handling

Commercial vehicles have a higher center of gravity than passenger cars. Because of this, commercial vehicles have an increased risk of rollover. Tankers have some of the highest centers of gravity and a correspondingly high risk of rollover.


In addition to a high center of gravity, tankers experience something called “surge.” Surge is caused when the liquid in the tanks moves around. Stopping causes the liquids to surge forward. When the liquid reaches the front of the tank, the truck is shoved forward—when the liquid surges back to the rear of the truck, the truck is shoved backward. Surge can cause a truck to be shoved forward or backward into a stopped vehicle. A truck can be shoved forward into an intersection. Stopping on ice can be especially challenging. Side-to-side surge can cause a truck to rollover.

You must be familiar with how the truck handles in both good conditions and bad conditions.


Some tanks are divided into smaller tanks using internal partitions called bulkheads. Commonly, there is one continuous tank body (shell) with one or more bulkheads running from side to side. This results in several small tanks; one in front of another. Examining fittings and fixtures can hint at how many of these smaller tanks a truck has. There will often be a specification plate attached to the tank, describing how much volume there is in each of the smaller tanks. Or, you can consult the owner’s manual to find this information.

Usually, each of these smaller tanks has a slightly different volume than any of the other smaller tanks. This causes the timing of the surge to be different for each small tank. The effect of surge is spread out over several seconds, reducing surge’s effect on driving. The danger of side-to-side surge is unaffected by bulkheads.

Be careful when loading bulkhead tanks. Don’t load all the weight in the front or the rear. Spread the weight out.


Some tanks have internal structures with holes in them called “baffles.” Baffles look like bulkheads, but they don’t divide tanks into smaller tanks; they are internal structures.

Surging liquid swirls through and around these baffles, increasing the time that the load is surging. This decreases surge’s effect on driving. Baffles help control front-to-rear surge. Usually, there are no side-to-side baffles.

Smooth Bore Tanks

A tank without baffles is called a smoothbore tank. There are no internal partitions to reduce surge. Smoothbore tanks are generally used when hauling food products. It is difficult to clean/sanitize tanks with internal structures. Most states require food to be hauled in smoothbore tanks. “Food” includes milk, fruit juice, wine, drinking water, etc.

Be especially careful when hauling smooth bore tanks.


When a liquid is heated, it expands. A tank that is completely full will overflow when the load warms. Leave extra room in the top of the tank for this expansion. This extra room is called outage. Various liquids expand at different rates. Know how much outage is required.

A Full Load

The maximum amount of liquid that can be transported in a tank is controlled by many factors:

  • weight of the liquid
  • maximum weight limits allowed on public roads
  • the truck’s Gross Combination Weight Rating (GCWR)
  • volume capacity of the tank(s)
  • how much the load will expand
  • temperature of the load

Some dense loads will “max out” weight limits before the tank’s volume is filled. In these cases, the tank(s) will be partially loaded. Partially loaded tanks make the surge situation worse.

Local Rules

Some states have additional restrictions regarding tankers. For instance, in California, if you are driving a tank vehicle loaded with a flammable liquid:

  • Speeding carries a stronger penalty.
  • Hours of service are reduced.

Safe Driving

Tankers are even more likely to roll over than a normal commercial vehicle. Tankers have a higher center of gravity. Tankers are subject to front-to-back surge and side-to-side surge. Therefore, you need to adhere to these safe-driving guidelines:

  • Drive smoothly.
  • Start, slow down, and stop with care.
  • Change lanes slowly and with care.
  • Brake early.
  • When braking, keep steady pressure on the brakes.
  • Do not release your brakes early (when stopping).
  • Expect surge to push you forward.
  • Increase following distance.
  • Know how much room it takes to stop.
  • If you must make a quick stop, use controlled or stag braking.
  • Do not steer quickly. (This could roll the truck on its side.)
  • Slow before curves and accelerate slightly through the curve.

The posted speed on corners is for cars on dry pavement with good traction. All trucks should drive slower than the posted speed on corners. Tankers should drive even slower than other trucks.

On wet roads, double the stopping distance. Empty vehicles can take longer to stop than loaded vehicles.


Do not oversteer, overaccelerate, or use excessive braking. These things can cause a truck to skid.

If your vehicle starts to skid, take corrective action. A skidding vehicle can jackknife.

If your vehicle starts to jackknife:

  • Release the brakes to restore traction.
  • Reapply the brakes.

Testing Hint

The following unrelated facts about tunnels might be referenced in the written DMV test for Tankers:

  • Be prepared to remove sunglasses when entering a tunnel.
  • Expect sudden gusts of wind when exiting a tunnel.

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