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How Do Hydro Excavation Services Work

How Do Hydro Excavation Services Work?

Before hydro excavation, the only way to remove dirt to create a trench or hole was to dig physically. For millennia, this was done by hand, with teams of workers using shovels and picks to loosen and remove soil and rock.

As engine-driven machinery became the standard, excavators and other digging equipment largely replaced such demanding physical labor. However, there were still two problems with using such machinery.

First, it can be dangerous to the workers. If an operator were distracted or a worker stepped into the wrong area, the result could be severe injuries or even death. Second, it can quickly destroy underground utilities, and the equipment could tear through if the crew were wrong about placing underground power lines or pipes.

The solution to these hazards came in the form of hydro excavation. Hydro excavating reduces the danger to both crews and buried utility lines.

What is hydro excavation, and how does it work?

How Does Hydro Vacuum Excavation Work?

Hydro excavation relies on pressurized water to loosen soil and a hydro excavator truck, or hydro vac, to vacuum the sludge into a container tank. The hydro vac can then haul this sludge to dump at a different location.

This process reduces risk to laborers and utility lines and makes for much cleaner digging — the hole or trench can be carved out to exact dimensions, even if underground utilities are in the way.


The hydro excavation also made daylighting far more accessible than ever. “daylighting” refers to uncovering underground pipes for maintenance, repair, or replacement purposes. In other words, the lines are exposed to daylight.

While crews formerly had to rely on precise digging, often wholly by hand, a hydro vac can accomplish the same task more efficiently.


Daylighting is one of many tasks made faster with hydro excavation. Trenching is a laborious process, even with an excavator. Hydro vac can create trenches of uniform depth and width in a fraction of the time, even on cold or frozen surfaces.

Removing Debris

One significant advantage of using hydro excavation for debris removal is the more efficient use of space. Instead of having excavators dig and drop the debris into a separate truck, one hydro vac can pick up and haul the debris by itself.

Digging Piling Holes

Thanks to its power and precision, hydro excavation is excellent for creating holes of specific widths and depths for pilings.

What Are the Benefits of Hydro Excavation?

Crews used to rely on traditional excavation techniques can benefit from the advantages of hydro excavation. Here are some of the biggest.

Less Environmental Impact

Hydro vac causes minimal disruption to the ground compared to other excavation techniques. Only one vehicle is needed for the job instead of several, saving on fuel and reducing emissions.

They also have much less environmental impact thanks to their precision and ability to remove dirt, rock, and other materials using only a concentrated stream of water.

Better Safety for Workers

Minimizing the amount of time and equipment required to accomplish the task of digging also reduces the possibility of injury. Hydro excavator trucks are inherently safer than large digging apparatuses since workers don’t have to worry about a bucket or shovel hitting them due to operator distractions or other errors.

Less Manpower Required

With the reduced need for equipment comes a reduced need for workers. A handful of employees can operate a hydro vac and get the same results as a larger team using traditional excavation equipment.

Less Disruption to Underground Utilities

Sewer pipes, septic tanks, power lines, and internet lines may lie buried in the ground that’s about to be dug up. If workers aren’t aware of their presence, an excavator or other digging machine could easily damage them, sometimes irreparably. Using a hydro vac, crews can expose these underground utilities without harming them.

Digging in Cold Weather

With a hydro vac, all digging becomes much more straightforward in cold weather. That’s because they rely on heated water, which allows them to melt the frozen dirt before suctioning it up.

Hydro excavation is exceedingly popular in Canada for this exact reason. Whereas traditional excavation techniques have often proved inadequate, the hot water used in hydro excavation has been highly successful in areas with colder climates.

Alternatives to Hydro Excavation

There are certain situations in which water might not be the best choice for excavation. Perhaps the area is sensitive to moisture, or your crew needs the hole or trench to be dry for their intended purpose. In these cases, you might consider air excavation,

Air excavation, also known as dry excavation, uses compressed air rather than water to disrupt the soil. Once the blasted air has sufficiently loosened the earth, the truck vacuums up the debris. One advantage air excavation has over hydro excavation is that the soil isn’t wet, which means the hole or trench can be backfilled later.

Air excavation is also the preferred method when digging around underground utilities, and this method presents much less chance of harming pipes, wires, or other buried items; with that being said, since air excavation requires more work time and larger crews, it’s usually more costly than hydro excavation.

Another alternative to hydro excavation is traditional excavation. However, because of how slow, tedious, and inefficient machine digging tends to be, it should only be used as a last resort.

What Is a Hydro Excavation Truck?

A hydro excavation truck, often called a hydro vac or vac truck, is simply a truck with the appropriate equipment attached to perform hydro excavation. Hydro excavation trucks feature several main components:

1. High-Pressure Water Hose and Water Pump

The crew operating the hydro vac uses this hose to loosen the soil. While some hydro vacs may carry their water to the work site, they may need a water source like a hydrant or water truck for longer jobs.

Hydrovac water pressure should never exceed 3,000 pounds per square inch (PSI) — too much stress can destroy buried lines and pipes.

2. Suction Hose and Vacuum Pump

Hydro vac removes the sludged dirt and debris from the hole via a special suction hose and vacuum pump. A hydro vac suction hose function works similarly to a standard vacuum cleaner.

3. Debris Tank

After suctioning it up, the truck transfers the loose soil into a debris tank and holds it there until it’s ready to be dumped. If the hydro vac needs to continue working on a tight schedule, some of the soil can be offloaded to allow another vehicle to take care of the dumping.

4. The Water Tank

Not being near a water source isn’t an issue for hydro excavation trucks, as nearly all hydro vacs feature an onboard water tank with an adequate capacity for most jobs.

Hydro vacs come in different sizes depending on the job they’ll be performing, and they’re usually measured in terms of their debris capacity — in yards.

The following sizes aren’t universal, but they’ll give you a good idea of the capabilities of various hydro vacs:

7 Yards

A machine of this size can remove approximately seven cubic yards of material and may hold 600-700 gallons of water. This type of hydro vac is primarily used for digging post holes.

10 to 15 Yards

Hydro vac with a capacity of 10-15 cubic yards also holds 1,200-1,500 gallons of water. These are generally sufficient for trenching and deep excavation.


Hydro vac can weigh quite a bit more than you might expect. Water is heavy, and larger machines can weigh more than 80,000 pounds when their tanks are full of soggy, saturated earth. With that in mind, choosing the most prominent model is only sometimes wise when selecting the suitable hydro vac for your project.

Hydrovac Trailers

While many hydro vacs serve as trucks and vacuuming equipment in one, some manufacturers provide hydro vac trailers. These allow crews or individuals to hook up an existing vehicle to a hydro vac trailer without investing in an entire hydro excavation truck.

The downside of hydro vac trailers is that they may only sometimes be available in the exact sizes a crew needs.

Choosing a Hydro Excavating Service

The most important thing to remember when choosing a hydro excavating service is that tools are only as good as their users. While hydro vac and air excavators pose much less risk to workers and the environment than traditional equipment, that doesn’t mean they’re 100% safe.

Any device designed to remove massive quantities of the earth will present specific hazards, so the crew you hire to perform hydro excavation must be skilled and experienced.

Hydrovac operators also need to understand bridge laws and dump site regulations. Bridges, even sturdy ones that have been standing for decades, can strain under the weight of a full hydro vac. For this reason, each state has laws governing the maximum size and weight of vehicles traveling or parking on bridges.

Excavation crews must be knowledgeable about dump site rules as well. Hazardous waste regulations are often strictly enforced. As such, your team should know how to operate within their constraints.

Lastly, hydro vac operators must be able to evaluate ground conditions. Crews need to quickly determine how effective a machine of a particular size will be when performing the job at hand and whether it can easily traverse a given patch of terrain.

Trust AOTC

When you need a skilled and experienced hydro vac team, AOTC should be your first choice. We have the equipment, skills, and know-how to provide the hydro excavation services you need.

We also offer Emergency Spill Response Services, meaning we’re ready, willing, and able to handle delicate cleanup jobs. Our crew is on standby 24 hours a day to deal with industrial chemicals, biohazards, spilled fuels, and other dangerous substances.

Whether you need to dig a trench or clean up after a disaster, AOTC is here to help and has the gear and skills required to get the job done right.


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