Some Liquid Tanks Are Divided Into Smaller Tanks By: The Answer

TLDR

Some liquid tanks are divided into several smaller tanks by bulkheads, the internal partitions that split one long tanker barrel into separate compartments. Where those partitions have holes that let liquid pass, they are called baffles, the surge-taming variant of the same wall.

Last updated September 2026.

The Answer, Explained for Real Drivers

If you are preparing for the CDL tanker endorsement, you have almost certainly met this completion question: some liquid tanks are divided into several smaller tanks by what? The accepted driver-manual answer is bulkheads. This people-first guide gives you the graded answer up front, then explains the hardware inside the barrel, the physics of liquid surge in plain words, and the driving habits that keep any liquid load stable. LowestPriceTrafficSchool.com is a leading destination for traffic school, defensive driving, and commercial permit prep, and everything below is written the way a careful instructor would say it out loud: qualitatively, practically, and with exact figures and test values left to your official state CDL manual, because those specifics vary by state.

What Are the Walls That Divide a Liquid Tank Into Smaller Tanks?

The accepted answer is bulkheads. A bulkhead is an internal partition fitted inside a structure to divide it into separate sections, and inside a tanker trailer it splits one long barrel into individual, self-contained compartments (Wikipedia).

Bulkheads: Sealed Walls That Create True Compartments

A bulkhead is a solid wall set across the inside of the tank. Each compartment it forms behaves like its own small tank, with its own valves and fittings, so a single trailer can carry several different but compatible products at once and unload them one at a time. Bulkheads also change how the load sits on the vehicle: instead of piling all of the liquid weight at a single station of the frame, they spread it along the length of the trailer, and each wall braces the shell against the pressure of the cargo it holds. That combination of separate products, balanced weight, and structural support is why the compartment tank is a standard design for delivery tank trucks (Wikipedia).

Baffles: Holed Walls That Tame Surge

A baffle is the same idea with openings in it. Where a bulkhead is sealed, a baffle lets liquid pass through slowly, which calms the front-to-back rush of a wave without stopping it completely (Wikipedia). Because liquid can still move through the holes, a baffled tank does not divide the cargo into separate products, and it still allows side-to-side movement. The driver feels the load lean in a curve even when the tank is heavily baffled, which is why baffles are described as surge reducers rather than surge eliminators. For a deeper look at how these holed walls work, see the guide to baffled liquid tanks and bulkheads.

Why Are Some Tanker Trailers Divided Into Compartments?

Compartment tanks exist for practical business and safety reasons, and every one of them traces back to what a wall inside a barrel can do.

• Multiple products on one run: a delivery driver can haul different compatible liquids at the same time, each sealed in its own compartment with its own valves, and serve several stops without returning to the terminal.
• Load spread along the vehicle: dividing the cargo distributes the weight across the frame instead of concentrating it, which supports steadier handling and legal axle loading without a separate scale visit for every product.
• A stronger shell: every internal wall braces the tank against the push of the liquid it holds, so a divided barrel resists the stress of a moving load better than an empty, unsupported one.

Fuel delivery is the classic illustration. A tanker serving a service station commonly carries several grades of product at once, each riding in its own compartment, and the driver opens one set of valves at a time. None of that works without bulkheads turning one big barrel into a row of smaller tanks.

How Liquid Surge Moves an Undivided Tank

Liquid is a moving cargo. Every brake application, every curve, and every grade change sends it sloshing, and in an undivided tank the whole mass surges from end to end and rocks the tractor long after the maneuver is over. The wave travels down the barrel, hits the forward wall or the rear head, and pushes against the vehicle as a shove that arrives a moment after the input that caused it. A partially filled tank is the hardest case, because the open space above the liquid gives the wave room to build. Solid bulkheads stop that front-to-back rush entirely, since liquid in one compartment cannot travel into the next. Baffled walls slow the same rush down, bleeding the wave through their openings, but they never stop it, and neither design does anything about side-to-side movement in a curve. That is the honest physics behind the test question, and it is why hardware and driving habits have to work together.

How to Handle Any Liquid Tank: Habits That Work With or Without Bulkheads

Compartment or no compartment, the safe-driving habits are the same, and examiners expect you to describe them in plain, practical terms.

1. Slow down before the curve: reduce your speed on the straightaway, then steer gently through the turn, because a wave created mid-curve pushes the tank sideways exactly when the vehicle is already leaning.
2. Brake and accelerate gradually: smooth pedal work keeps the load from rushing to the front or rear of the tank, and it matters just as much in a baffled tank as in a bulkheaded one.
3. Keep extra following distance: a tanker needs room to react, and a long cushion lets you respond to traffic without the sudden inputs that turn cargo into a battering wave.
4. Respect a partial fill: remember that a partially loaded compartment surges worst of all, so treat a half-full tank as the most demanding load you will drive all day.
5. Check your own state manual: exact test figures, endorsement requirements, and tanker rules come from the official CDL manual and your state DMV, and they vary from state to state, so always confirm the specifics where you will test.

Common Tanker Question Mistakes to Avoid

Mistake 1: Confusing Baffles With Bulkheads on the Test

The graded answer to the divided-tank question is bulkheads, and a vague answer loses the point. A weak response says the tank is divided by walls; a strong response names bulkheads as the partitions that create the compartments, then adds that baffles are the holed walls that tame surge. Learn the pair together so the distinction is automatic, using the CDL tanker endorsement test guide to drill the wording.

Mistake 2: Assuming Divisions Remove Surge Risk Completely

Bulkheads stop front-to-back surge, and baffles slow it, but neither makes the load rigid. Liquid still leans side to side in a curve, a baffled tank still passes liquid through its openings, and a compartment that runs partially empty on a delivery route surges harder than it did when full. Drivers who treat hardware as a substitute for smooth driving recreate the exact hazard the endorsement exists to prevent.

Mistake 3: Treating Every State Rule as Identical

The physics never changes, but the paperwork does. Endorsement procedures, testing steps, and handbook wording are set state by state, so a study plan copied from a friend in another state can miss what your DMV expects. If you are testing in Florida, for example, the Florida tanker endorsement guide walks through how that state handles the process, and the same principle applies everywhere: confirm with your own state DMV.

Get Tanker-Ready With LowestPriceTrafficSchool.com

LowestPriceTrafficSchool.com supports drivers at every stage, from the first permit to the tanker endorsement and back down to everyday defensive driving courses for ticketed motorists. If you are chasing the endorsement, start with the CDL tanker endorsement test guide, then read the baffled liquid tanks article until the bulkhead-versus-baffle distinction is second nature, and finish with the state guide that matches where you will test. If you are a regular driver in Florida handling a citation instead, the same site's traffic school and defensive driving courses are the straightforward path to refreshing your skills. Either way, the approach is identical to this article: the accepted answer first, the reasoning behind it next, and the habits that keep you safe on the road last.

Frequently Asked Questions

Some liquid tanks are divided into several smaller tanks by what?

The accepted driver-manual answer is bulkheads, the internal partitions that split a tanker barrel into separate compartments. Where those partitions have holes that let liquid pass through slowly, they are called baffles.

What is the difference between a bulkhead and a baffle?

A bulkhead is a sealed wall that divides a tank into true compartments and stops front-to-back surge entirely. A baffle has openings, so it slows liquid movement but never stops it.

Why do tanker trailers have multiple compartments?

Compartments let a single trailer carry several compatible products at once, each with its own valves. They also spread the liquid weight along the vehicle and brace the tank shell against the load.

Do baffles completely stop liquid surge in a tank?

No. Baffles slow the front-to-back rush of liquid and soften each wave, but a baffled tank still allows side-to-side movement, so drivers must still handle curves and brakes gently.

Which liquid load surges the worst?

A partially loaded tank or compartment surges worst, because open space gives the liquid room to build a wave. Full compartments surge far less, though smooth driving remains essential either way.

Citations

• https://en.wikipedia.org/wiki/Tank_truck
• https://en.wikipedia.org/wiki/Baffle
• https://en.wikipedia.org/wiki/Bulkhead_(barrier)