How Does Hydro Excavation Work?

Hydro excavation, or hydrovac as it is sometimes called, is the fastest, cleanest and safest way to dig that removes the least amount of material in a safe manner. Since it does not use mechanical methods, utility facilities such as buried pipe and cables are left undisturbed and undamaged.

Hydrovac Equipment

Hydro excavation services are usually truck or trailer mounted. It is comprised of several basic components:

  • A large water reservoir
  • A larger debris tank
  •  An 8 inch diameter suction hose attached to a swinging pivot
  • A cyclone vacuum unit
  • A high-pressure water system with wand
  • An onboard water heater


Water storage capacity is typically 4500 liters. The debris tank holds over 10 cubic meters of slurry and is mounted on a tilt bed for easy debris disposal. The water pump produces 40 MPa at 34 l/sec volume. The hydro vacuum excavation unit creates 150 cubic meters of suction per minute. Around 400,000 BTUs of water heating capacity is also available.

How It All Works Together

The water wand injects a highly pressurized stream of water at the point to be excavated. As the surrounding soil liquefies, the slurry is transported to the debris tank via the vacuum hose. Any type of soil can be extracted in this manner including dry or wet clays, silt, sand, gravel and common fill materials.

The high-pressure wand allows for almost surgical precision in cutting through the ground, which reduces the amount of material excavated compared to mechanical means. If the ground is frozen, the water stream can be heated.

The Advantages of Industrial Hydro Excavation

Sometimes, hydro excavation is criticized as being more expensive than a conventional excavator on a cubic meter basis. However, a direct comparison is misleading since hydrovacs remove far less material to accomplish the same purpose. Furthermore, since the risk of damage is drastically reduced compared to mechanical means, the high costs of repairing damaged utilities or the potential for the creation of a life-threatening situation are avoided.

Using hydro excavation companies – and their hydrovac services –  has other practical advantages as well:

  • It can dig to depths of 20 meters or more
  • It can be used in space constrained areas via hose extensions up to 200 meters from the truck
  • Workers remain on top of the hole instead of inside it
  • Debris is not piled to one side, but instead safely conveyed to the debris tank

Hydro Excavation Applications

Beside “daylighting” existing utility lines and cables, hydro excavation has a large number of additional applications across industries:

  • Slot hydro trenching for installation of cables, waste or supply lines and sprinkler systems
  • Excavation of holes for signs, poles or pilings
  • Debris removal from slides or tunnel collapses
  • Re-mapping of utility installations for municipal subsurface utility engineering
  • Digging test holes for horizontal boring projects
  • Installation of water main sacrificial anodes
  • Industrial tank cleanout

When you consider that all these jobs can also be accomplished during freezing weather, it is easy to see why industrial hydrovacs are increasingly considered best practice for any excavation job.

A Better Method Overall

As the superiority of hydro excavation has become better known, more municipalities are mandating its use over mechanical excavation due to its increased accuracy and its 100 percent avoidance of utility strikes. All factors considered, compared to mechanical excavation, hydro excavation is simply less expensive, less time consuming and safer.

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