Post Hole Digger

Digging Deep, Straight, Uniform Holes with a Shop-Vac


Fence Post Hole Digger

Digging Deep, Straight Uniform Holes with a Shop-Vac

Digging deep, straight, uniform holes with a Shop-Vac especially with the new vacuum assisted Holey-Moley Digger invention is now easy and affordable. While digging holes with a Shop-Vac is not a novel idea, it is a very effective way to save your back and prevent sore muscles from repetitious use of hand tools. If you have a shallow hole to dig, or some dirt to pickup or to move, especially if it is located in a place where it is hard to manipulate hand tools, a shop vacuum may be the right tool for you.  Should you want to dig deep, straight, concentric holes a vacuum assisted Holey-Moley Digger is the lowest cost, most effective means of doing the job.  If you haven’t used a shop vacuum to dig deep, straight, concentric holes before, here are a few useful hints to make the job easier.

1. Filters

The first thing when digging holes with a shop-vac is to use a good filter or to wear a dust mask. There are many microbes in the soil and you will be breathing a lot of dust if you are not wearing a mask. In addition to a facemask using a good HEPA filter with your shop vacuum will significantly reduce the dust in the air.

Filters will get clogged relatively fast when vacuuming up dirt which slows down the dirt uptake process, so periodically turning off the vacuum, removing the lid and banging the filter on the side of the vacuum will knock off most of the dirt. This is where the face mask comes in handy.

You will need to empty the shop vacuum of soil before it gets too heavy, so this is a good time to bang the filter on the side of the vacuum container to loosen up the dirt building up. For dirt that is more resistant, or slightly moist, you may have to remove the filter to bang the dirt out. Most shop vacuums come with a diverter at the end of the hose where a bag is connected. This will divert the dirt down about 45 degrees and protects the filter. If the digging speed slows down, clean the filter.

2. Hoses

Hoses for shop vacuums are typically sized to optimize system performance. Vacuum cleaners will typically pull an 80% vacuum when completely shut off at the suction end; however, this rapidly drops off, as the end is opened to the atmosphere. For moving dirt, the larger diameter hoses work better. For most conditions 2-1/2 inch to 3 inch hoses work best for picking up dirt, sand, and gravel.


digging-deep-straight-uniform-holes-gravel-up-to-1.5 inches-picked-up-with-a-Shop-Vac
Gravel up to 1.5 inches is easy to pick up with a shop-vac with 2-½ inch or larger hose


3. Soil Weight

Dirt weighs in at 10-lbs/gal dry for loose dirt and up to 16 lbs/gal for wet sand. Soil weight adds up fast in a shop vacuum and becomes hard to lift with only a few gallons of dirt.  A ten-gallon shop vacuum filled with soil can weigh in at 100 to 160 lbs and becomes a bear to handle.  As a rule of thumb, roughly 2 to 3 gallons of soil is within the realm of easy lifting and dumping. Figure 50 lbs for a 5-gallon bucket. Dumping the contents into a wheelbarrow when you accumulate a few gallons of dirt makes it much easier to handle. For a 6-inch diameter hole, figure about 6 gallons of loose soil per foot of depth.

The following table lists the density and weight per gallon of various soils for reference:

Soil Weight Reference Chart


Dirt Loose Dry

Dirt Loose Moist


Sand dry

Clay dry

Clay wet

Sand Wet

Gravel Wet

Density (lb/ft3)









Wt (lb/gal)










Check out the Hole Volume Calculators for calculating the hole volume in cubic feet and gallons, the weight of the material removed from the hole, and the swell volume of loose material after it is removed from the hole.

4. Shop Vacuum Rating

Most shop vacuums will vacuum up dirt. However one attribute of a shop vacuum that stands out over everything else, when picking up dirt, is flow rate. You will find flow rate  listed in (CFM) – Cubic Feet per Minute of airflow. This measurement is done at the vacuum inlet without any restriction. As a result, the greater the CFM rating the better. Finally, shop vacuums with 180 to 200 CFM ratings are more than adequate for digging holes.

Many shop vacuums will show or list horsepower, which is quite misleading as the HP is usually done in a laboratory and is the horsepower at stall speed of the motor. A better way to look at power is to look at watts. You can observe the rated wattage by looking at the amp rating of the vacuum cleaner.  Wattage stickers are usually near the vacuum motor.

The largest shop vacuums have ratings at 12 amps. Since volts x amps = watts and the voltage is assumed to be 120 volts, the amp rating is more than adequate for comparing shop vacuum. A good rule of thumb is the higher the amp rating the more power the vacuum has for digging. A shop vacuum with a 12-amp rating, a flow rate of 180 to 200 CFM, and a 2 to 2-1/2 inch hose should be more than adequate for digging.

5. Wheels and Handle

A typical shop vacuum does not move well in a garden. Small wheels and excessive weight make them useless for moving dirt from one location to another. When digging holes with shop vacuums with small wheels, it is best to empty the container into a wheelbarrow for transporting. However, a number of shop vacuums, usually listed as Contractor, Professional, or Industrial models, have large rear wheels and a handle. As a  result, these will usually handle 100 lbs to 200 lbs of weight.  In addition they are easy to move over dirt or lawns. These professional or contractor models typically have 12-amp ratings with larger hoses in the 2 inch to 2-1/2 inch range.


Industrial shop-vac
Industrial model Shop-Vac with larger wheels and handle



Author's Shop-Vac with 2-inch hose
Author’s Shop-Vac rated at 12 amps with 2-½ inch hose


Portable Engine Driven Shop Vacuum System
Portable Engine Driven Shop Vacuum System


6. The Soil in your Shop-Vac

When digging holes with a shop vacuum, a variety of tools will loosen up the soil making it easy to vacuum up.  After you remove soil,  some may be put back into the hole. In addition, dumping the soil out on a tarp works well for mixing in planting soil. You will also find that the soil inside the vacuum will have a very fine consistency. Therefore it is easy to separate out rocks and heavy gravel. A pea gravel screen on top of a wheelbarrow works well for this task.  Should you be allergic to dust, you might want to wear a dust mask while working with the fine dust created during the vacuum process.  The dirt in the shop vacuum will have a very fine consistency.


A pea gravel screen works well for separating gravel from dirt


Dirt vacuumed out of a hole has a very fine consistency


In the end, you will find that a shop vacuum makes the task of digging deep, straight, uniform holes much easier. In addition, it is cleaner, and usually faster than digging with a hand tool. A Shop-Vac will give you more control so you can dig deep, straight, uniform holes in minutes.  In addition, you will also have the shop vacuum for cleaning up the work site. If you have a wet-dry vacuum, you can wash the unit up with a garden hose before storing.

7. Digging Deep, Straight, Uniform Holes

The Digger produces straight, uniform holes 4″ to 12″ in diameter


The affordable Holey-Moley Digger is shown in the cover photo.  This is an example of a post hole digger capable of digging holes 15 to 20 feet deep or more.  In addition, the Digger is available in 4-inch, 5-inch, and 6-inch diameters.  As a result, you can dig deep, straight, concentric holes for posts which reduces concrete requirements.  Therefore you save time and money. Finally, if you need larger holes for poles or concrete tubes, 6-inch holes can be made larger using the EZ Reamer for 8″ holes, or larger with our 10-12″  Hole Reamers.


Digging holes with a shop vacuum saves time and money by reducing the size of holes. Therefore, using a shop vacuum where it counts on removing material is key.  Finally, the efficiency of a shop vacuum is to increase by keeping filters clean, reducing hose length, and increasing hose diameter.  When looking for a shop vacuum consider the soil weight, which can weigh between 75 and 150 pounds. Also, make sure the wheels and handle can handle the weight of material you are going to remove from the hole.  In conclusion, use a Holey-Moley Digger to dig deep straight uniform holes to save time and money.


More Articles on Digging with the Holey-Moley Digger:

Selecting The Best Hole Digging Shop Vacuum

Can Your Little Shop-Vac Suck Rocks Up?

Ridgid Shop Vacuum WD19560 Comparison Test

Tangential Gas Powered Vacuum Filter Bucket

Other links you may enjoy:

Leave a Reply

You must be logged in to post a comment.