How many questions are on the tanker test?

Each state sets the number, but Washington and Illinois both use 20 questions. You need 16 correct to pass.

Is there a skills test for the tank endorsement?

No. Federal rules require only a knowledge test for the tank vehicle endorsement.

Outage is the empty space left at the top of a tank so the liquid can expand as it warms. Never fill a cargo tank all the way.

CDL Tanker Endorsement Practice Test 2026

Q: When do I need a tanker endorsement?

When you haul any liquid or gas in tanks rated over 119 gallons each and 1,000 gallons or more in total. The liquid does not have to be hazardous.

Question 1 of 25

Under the CDL rules, a tank vehicle carries liquid or gas in tanks of what size?

Any single tank of 500 gallons or more
Each over 119 gallons, and 1,000 gallons or more in total
Each over 50 gallons, and 500 gallons or more in total
Only tanks of 5,000 gallons or more

Show answer

Answer: B. Each over 119 gallons, and 1,000 gallons or more in total

You need a tank endorsement when individual tanks are rated over 119 gallons and the total is 1,000 gallons or more.

Question 2 of 25

A truck carries three tanks of 400 gallons each, filled with water. Does the driver need a tank endorsement?

Yes: each is over 119 gallons and the total is 1,200
No, because water is not a hazardous material
No, because no single tank holds 1,000 gallons
Only if the truck is fitted with air brakes

Show answer

Answer: A. Yes: each is over 119 gallons and the total is 1,200

Each tank is over 119 gallons and together they hold 1,000 gallons or more. The liquid does not have to be hazardous.

Question 3 of 25

A truck carries ten 100-gallon tanks of liquid. Is this a tank vehicle under the CDL definition?

Only if the liquid is fuel
Yes, any tank truck counts
No, because no single tank is over 119 gallons
Yes, because the total is 1,000 gallons

Show answer

Answer: C. No, because no single tank is over 119 gallons

Both parts of the definition must be met: tanks over 119 gallons each and 1,000 gallons or more in total.

Question 4 of 25

Does the liquid in a tank vehicle have to be hazardous for you to need the tank endorsement?

Only gases count
Yes, only hazardous liquids count
No, any liquid or gas counts
Only flammable liquids count

Show answer

Answer: C. No, any liquid or gas counts

The tank endorsement is about the tank, not what is in it. Milk or water in a large tank counts.

Question 5 of 25

Do tanks that are only temporarily attached to a vehicle count for the tank endorsement?

Only if they are welded in place
No, only permanent tanks count
Yes, temporary tanks count too
Only if they are completely full

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Answer: C. Yes, temporary tanks count too

The endorsement applies to tanks that are either permanently or temporarily attached to the vehicle.

Question 6 of 25

A Class C vehicle carries hazardous liquid in tanks large enough to be a tank vehicle. What does the driver need?

Tank and hazmat endorsements
Only a passenger endorsement
No endorsement
Only a doubles endorsement

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Answer: A. Tank and hazmat endorsements

Class C drivers need the tank endorsement when hauling hazardous materials in liquid or gas form in tanks of that size, plus the hazmat endorsement.

Question 7 of 25

What kind of test is needed for the tank vehicle (N) endorsement?

A skills test only
A knowledge test and a road test in a tanker
No test
A knowledge test

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Answer: D. A knowledge test

The tank vehicle endorsement requires a knowledge test.

Question 8 of 25

What does the X endorsement mean?

You may pull triple trailers on highways
You passed both the tank and hazmat tests
You may drive any type of commercial vehicle
You are allowed to give CDL skills tests

Show answer

Answer: B. You passed both the tank and hazmat tests

The X endorsement combines tank vehicle (N) and hazardous materials (H).

Question 9 of 25

A CLP holder has an N endorsement on the permit. What may they drive?

Tank vehicles under 5,000 gallons
Any tank vehicle with a CDL holder present
Only an empty tank vehicle
Tank vehicles carrying water only

Show answer

Answer: C. Only an empty tank vehicle

A CLP holder with an N endorsement may only operate an empty tank vehicle.

Question 10 of 25

When should you inspect a tank vehicle?

Only when you see a leak
Before loading, unloading or driving
Only after you finish unloading
Only once a week, at the yard

Show answer

Answer: B. Before loading, unloading or driving

Inspect the tank vehicle before you load, unload or drive it.

Question 11 of 25

What is the most important thing to look for when inspecting a tank vehicle?

Dents in the cab
A clean windshield
Leaks under and around it
Mud on the tires

Show answer

Answer: C. Leaks under and around it

Check for leaks anywhere on the vehicle. Carrying product in a leaking tank is a crime.

Question 12 of 25

What can happen to a driver who carries liquid in a leaking tank?

Nothing, as long as the leak is small
Only a warning, the first time it happens
Nothing; only the shipper is responsible
They can be cited and made to pay for cleanup

Show answer

Answer: D. They can be cited and made to pay for cleanup

A leaking tank is treated as a crime. You can be cited, kept from driving further, and made liable for the spill cleanup.

Question 13 of 25

What should you check on the intake, discharge and cut-off valves?

That they are freshly painted
That they are in the correct position
That they are removed for cleaning
That they are all fully open

Show answer

Answer: B. That they are in the correct position

Make sure all valves are in the right position before loading, unloading or moving.

Question 14 of 25

What should you check on manhole covers?

That they are removed while driving
That they are open for air
That they are locked open
That they have gaskets and close properly

Show answer

Answer: D. That they have gaskets and close properly

Manhole covers must have gaskets and close correctly. Keep the vents clear.

Question 15 of 25

Which of these is special equipment you may need to check on a tank vehicle?

A trailer hitch ball
A sleeper berth
Grounding and bonding cables
Snow tires and chains

Show answer

Answer: C. Grounding and bonding cables

Tank vehicles may have vapor recovery kits, grounding and bonding cables, emergency shut-off systems and built-in fire extinguishers.

Question 16 of 25

Can you drive a tank vehicle with a valve or manhole cover open?

Yes, if the tank is empty
Yes, on short trips
Yes, for ventilation
No, never

Show answer

Answer: D. No, never

Never drive a tank vehicle with open valves or manhole covers.

Question 17 of 25

Why do tank vehicles roll over more easily than many other trucks?

They are always driven empty
They have no suspension at all
They have very small tires
They have a high center of gravity

Show answer

Answer: D. They have a high center of gravity

Most of the load's weight sits high above the road, which makes the vehicle top-heavy.

Question 18 of 25

How should you take curves and ramps in a tank vehicle?

In neutral
At the posted speed
Slightly above the posted speed
Well below the posted speed

Show answer

Answer: D. Well below the posted speed

Tankers can roll over at the posted speed limits for curves. Take highway curves and ramps well below posted speeds.

Question 19 of 25

What is liquid surge?

Liquid leaking out of a loose valve
Liquid moving back and forth in a tank
Liquid expanding in hot weather
Liquid freezing inside the tank

Show answer

Answer: B. Liquid moving back and forth in a tank

In a partly full tank, the liquid moves. This movement is called surge.

Question 20 of 25

Why is a partly filled tank harder to control than a full one?

The liquid has room to move and surge
It weighs more
It has a lower center of gravity
Its brakes are weaker

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Answer: A. The liquid has room to move and surge

Partly filled tanks let the liquid move, which can push the truck around.

Question 21 of 25

You stop a tank truck that is partly full. What can the surge do?

It pulls the truck backward only
The wave can push the truck forward
Nothing; the liquid stays still
It raises the pressure in the tank

Show answer

Answer: B. The wave can push the truck forward

When you stop, liquid surges forward and back. The wave can push the truck forward, even into an intersection on a slippery road.

Question 22 of 25

On an icy road, why is surge especially dangerous?

It locks the steering wheel in one position
It can push a stopped truck into an intersection
It turns off the brakes on the rear axles
It makes the liquid in the tank freeze faster

Show answer

Answer: B. It can push a stopped truck into an intersection

On slippery surfaces, surge can push a stopped truck forward. Know how your vehicle handles.

Question 23 of 25

What are bulkheads in a tank?

Covers over the hatches on top of the tank
Ladders on the side of the tank for climbing
Walls that divide the tank into compartments
Valves at the bottom of the tank for unloading

Show answer

Answer: C. Walls that divide the tank into compartments

Bulkheads divide a tank into smaller tanks. When loading, watch the weight distribution.

Question 24 of 25

When loading a tank divided by bulkheads, what must you watch?

That all compartments stay empty on the trip
Not too much weight at the front or rear
That the bulkheads are removed before loading
That every compartment is filled to the top

Show answer

Answer: B. Not too much weight at the front or rear

Pay attention to weight distribution so you don't overload the front or rear of the vehicle.

Question 25 of 25

What are baffles in a tank?

Bulkheads with holes that let liquid through
Hoses that connect two tanks together
Covers that seal the manholes on top
Solid walls with no openings at all

Show answer

Answer: A. Bulkheads with holes that let liquid through

Baffles are bulkheads with holes. They slow front-to-back surge.

CDL Tanker Endorsement Practice Test 2026

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