Hydro excavation and air excavation represent two fantastic digging methods, with benefits that make them incomparable to traditional digging.
In a side by side comparison, hydrovac is faster than air excavation; it cuts the earth faster, so it helps dig faster. However, if we evaluate these two methods further, we notice that things become more balanced. First, because a hydrovac truck must be constantly filled up with water and the refill process takes time, especially if water is not available near the working site, and the operator must drive certain distances to fill the equipment up. Meanwhile, air excavators use small amounts of water and can go on for days without being refilled. So, if the water source is not close by, using an air excavator is a better option.
Additionally, air excavation units are more efficient at pulling up dry debris, but hydro excavators are better for potholing and digging in cold weather, because water is heated and breaks easily frozen soil.
The bottom line is that great results can be achieved with both techniques. If you have a large area to excavate, have a water source close by or must excavate in cold weather, you may want to opt for water excavation. On the other hand, if you only dig small test holes that must be backfilled when the project is complete, then using an air excavator is probably a better alternative.