Do I need the tanker endorsement if the liquid is not hazardous?

Yes, if the tank size rules apply. The manual says the liquid or gas does not have to be a hazardous material.

How many questions are on the tanker test?

Your state sets the number of questions and the passing score. Federal rules set 80 percent as the minimum passing score for each knowledge test. Check your state's CDL manual.

What is the X endorsement?

X is the code federal rules list for a combination of the tank vehicle and hazardous materials endorsements. Check with your state licensing office on how it issues and tests for it.

CDL Tanker Endorsement Test: Who Needs It, What It Covers

You need the CDL tanker endorsement, called the N endorsement, if you drive a tank vehicle. The test covers inspecting a tank, how liquid moves inside it, and how to drive so it does not roll or skid.

Who needs the tanker endorsement?

Federal rules define a tank vehicle in 49 CFR 383.5. The definition says:

"Tank vehicle means any commercial motor vehicle that is designed to transport any liquid or gaseous materials within a tank or tanks having an individual rated capacity of more than 119 gallons and an aggregate rated capacity of 1,000 gallons or more that is either permanently or temporarily attached to the vehicle or the chassis."

Read the two numbers closely. Each tank must be more than 119 gallons. The tanks together must be 1,000 gallons or more.

The rule has one exception. It says: "A commercial motor vehicle transporting an empty storage container tank, not designed for transportation, with a rated capacity of 1,000 gallons or more that is temporarily attached to a flatbed trailer is not considered a tank vehicle."

The liquid does not have to be hazardous. The manual says so directly. Any liquid or gas counts if the tank size rules apply.

The manual says a tank endorsement is required if your vehicle needs a Class A or B CDL and you haul liquid or liquid gas in tanks that size. It adds that Class C vehicles also need it when used to transport hazardous materials in liquid or gas form in those tanks. Ask your state licensing office how it applies the rule to your truck.

What Section 8 covers

The manual says to study Sections 2, 5, 6 and 9 as well. Section 8 has three parts:

Inspecting tank vehicles. Leaks, valves, pipes, hoses, manhole covers and vents. Also special equipment like vapor recovery kits, grounding and bonding cables, and emergency shut-offs.
Driving tank vehicles. High center of gravity, surge, bulkheads, baffles, outage and how much to load.
Safe driving rules. Smooth driving, controlling surge, curves, stopping distance and skids.

Your state sets the number of questions and the passing score. The federal minimum is 80 percent on each knowledge test. Check your state's CDL manual for the rest.

Key points to know

Topic	What the manual says
Leaks	The most important item to check on every tank vehicle. Carrying liquids or gases in a leaking tank is a crime.
Valves and covers	Never drive with open valves or open manhole covers. Keep vents clear.
High center of gravity	Tankers can turn over at the posted speed for curves. Go well below it.
Surge	Liquid moves in a partly filled tank. It can push a stopped truck, even into an intersection on ice.
Baffled tank	Holes in the baffles let liquid through. They slow forward and back surge. Side to side surge can still roll you.
Smooth bore tank	Nothing inside slows the liquid. Forward and back surge is very strong. Common for food products like milk.
Outage	Never load a tank totally full. Liquid expands as it warms.
How much to load	Depends on expansion, the weight of the liquid and legal weight limits.
Wet roads	Double the normal stopping distance.
Empty tank	May take longer to stop than a full one.

The facts drivers miss

Surge works on you when you stop. When you brake, the liquid slides forward. When the wave hits the end of the tank, it pushes the truck the way the wave is moving. That is why the manual says to brake far in advance, keep steady pressure and not release too soon.

Baffles help in one direction only. Baffles are bulkheads with holes in them. They control forward and back surge. They do not stop side to side surge, and that can cause a rollover. Do not mix up baffles with bulkheads. Bulkheads divide a tank into smaller tanks, so watch weight distribution when you load and unload them. Don't put too much weight on the front or rear.

Smooth bore means no baffles. Sanitation rules forbid baffles in food tanks because they are hard to clean. The manual says to be extremely cautious, slow and careful, when starting and stopping.

Outage is room to expand. Different liquids expand by different amounts. You must know the outage requirement for what you haul.

A full tank can be too heavy. Dense liquids, such as some acids, can pass legal weight limits before the tank is full. You may often have to fill the tank only part way.

Rollover is the big risk. Much of the weight rides high off the road. The manual says to take highway curves and ramps well below the posted speed. Slow down before the curve, then accelerate slightly through it. If you steer quickly while braking, your vehicle may roll over.

Quick stops. If you must stop fast to avoid a crash, use controlled braking or stab braking. The manual sends you back to subsection 2.17.2 if you do not remember them.

Skids. Don't over steer, over accelerate, or over brake. On tank trailers, if the drive wheels or trailer wheels skid, the vehicle may jackknife. Act to restore traction to the wheels.

Tanker plus hazmat: the X endorsement

Federal rules list N as the code for a tank vehicle and H as the code for hazardous materials. They also list X as the code for a combination of tank vehicle and hazardous materials endorsements. If you plan to haul hazardous liquids in a tank, read our hazmat test guide. Ask your state how it tests for and prints the X.

Try 10 exam-style questions built from the official CDL manual.

Traps on the test

119 versus 1,000. 119 gallons is each tank. 1,000 gallons is the total.
"Hazardous" is not required. Harmless liquid in a big enough tank still needs the endorsement.
Baffles versus bulkheads. Bulkheads split a tank. Baffles have holes and slow surge.
Baffles do not fix side surge. Side to side surge can still cause a rollover.
Posted curve speed. It may be too fast for a tanker.
Empty is not safer. An empty tank vehicle may take longer to stop than a full one.

How to study it

Read Section 8 once. It is short. Then answer the "Test Your Knowledge" questions at the end of it out loud. Make a card for each row of the table above. The manual also says to study Sections 2, 5, 6 and 9.

After that, take practice tests and read why each wrong answer is wrong. If you are not sure which tests you need, see which CDL tests do I need.