Selecting The Best Hole Digging Shop Vacuum can be a difficult task, but it is worth taking the time to investigate because hole digging is one of the best uses for the shop-vac. This article will shorten your effort and even recommends using the old relic sitting in the corner of your garage first to get a little experience before purchasing a new one. Either way, old or new, digging holes with a shop vacuum is one of the best labor saving tasks that it does well.
Selecting The Best Hole Digging Shop Vacuum
by Titus Nelson, PE
With over a hundred shop-vacs available in the market place, Selecting The Best Hole Digging Shop Vacuum for can be a daunting task. This article should help you select a shop-vac that meets the requirements of the Holey-Moley Digger and works well for digging in the dirt as well as being within a reasonable price range. If you currently own a shop-vac, you should try digging with it first before going out and buying a new one. As a result, you will gain some experience with the concepts that are laid out here for selecting a vacuum.
Primary Specifications
The primary vacuum specification includes watts, amps, volts, water lift (or sealed suction), horsepower, air watts, and airflow. Other criteria that might be used to select a vacuum are filtration, cleaning tools (rotating brushes), capacity, quality, noise, cost, warranty, and features. The vacuum motor and the fan are the key components in a vacuum system.
Also, the more powerful the motor, the higher the speed, and the diameter of the rotating fan blades determine the airflow rate and suction level or differential pressure from inside the container and outside. The following review of typical shop-vac specifications should help when searching for good shop-vac to meet the requirements of the Holey-Moley Digger.
We also have some other good articles on Shop Vacuums:
Power Rating
Some manufacturers rate their shop-vacs in horsepower. Many have printed right on the front of the shop-vac the horsepower such as 6.5 HP which is quite misleading as this is the horsepower measured in a laboratory at motor stall speed, which will never be seen with normal use. A much better criterion to look for is the amp rating of the vacuum. A typical rating for a 6.5 HP vacuum might be 12 amps (volts x amps = watts) so a 12-amp vacuum running at 120 volts (your normal voltage supplied at most outlets) will use 1440 watts. At 746 watts per horsepower, this is hardly a 6.5 HP vacuum; it’s more like two horsepower.
Also, one must keep in mind that other components of a vacuum system such as power heads contribute to the amps used. So, try to compare vacuums by the motor watts. Hope this sheds some light on how you can be deceived with shopping for vacuums. So look for the amp rating that is usually marked somewhere on the motor plate or the motor housing. You might find this on the specification sheet.
Especially relevant is that the maximum allowable amp draw for an appliance that plugs into a standard household outlet is 12 amps. When comparing motors, either amps or watts can be used. Motor amp or watt ratings do not take into consideration the efficiency of the motor. Keep in mind that two motors of the same watt rating might have different flow rates.
Sealed Suction or Water Lift
A vacuum cleaner’s Sealed Suction or Water Lift is measured in inches of water lift and indicates how many inches the motor will lift a 1” column of water vertically when the vacuum inlet is fully closed. A vacuum cleaner’s power to pick up or “lift” debris is determined by sealed suction. On the other hand, airflow then removes it to the dust bag. If there is no airflow, the suction has no value in moving a particle.
Vacuum cleaners with more inches of water lift, additionally will have an easier time picking up sand and gravel, which is an indicator of the vacuum cleaner’s ability to overcome resistance of clogged or dirty filters. The sealed suction of a shop-vac is a useful means of comparing the suction of one motor to another. The more inches of sealed suction a vacuum cleaner has the better, with the tradeoff being higher cost for two stage motors.
Air Watts
Instead of comparing vacuums by their input power, some manufactures are providing the vacuum’s air output power in Air Watts. Air watts are the airflow times the vacuum. The formula is ((CFM x Inches of Water)/8.5) = Air Watts). This sounds like a good comparison, but in actual comparison, the air watt is approximately equal 99% of the input watts. For comparative purposes the higher the air watts the better.
Air Flow Rate
Air Flow Rate is the most important criteria when selecting a Hole Digging Shop Vacuum. Therefore, the higher the airflow rate a shop-vac has, the better. Measured in cubic feet per minute (CFM), flow rate is one attribute that most shop-vacuum manufactures publish on their specification sheets. The airflow rate is usually measured at the shop-vacuum opening with full, unrestricted airflow, with a clean filter.
Airflow is a good criterion when looking at digging ability of a shop-vac as it takes into consideration the power of the motor as well as the resistance of the system and the filter. Because the Holey-Moley Digger works best with the highest airflow rate at the digger head, we are not as interested in high static pressure vacuums. These are usually two-stage and cost quite a bit more. The key criterion to look for in a shop-vac is a high CFM rating. Generally, 150 to 200 CFM is more than adequate to operate the Holey-Moley Digger.
Hose Diameter
The Holey-Moley Digger has a 2-inch PVC pipe suction assembly. To keep the air flow rate up, your shop-vac should have a minimum 2-inch hose diameter. The hose diameter is normally supplied on the specification sheet or is written on the box. The best Hole Digging Shop Vacuum will have a minimum of 2-inch and preferably a 2.5-inch to 3-inch hose. Almost all of the shop-vac models that are classified as contractor, industrial, or professional, come with 2-½ inch hoses. In addition, the larger the hose diameter used, the easier it is to maintain a high system airflow rate. Hoses also have a resistance to airflow measured on a per foot basis. The shorter the hose and the bigger the diameter the better to reduce the resistance.
Filters
Filters play a significant role in shop-vac performance. Where a HEPA filters will significantly reduce the airborne microbes, and harmful dust particles that are released from the soils, they also increase the resistance to airflow. It is recommended that air masks be used when using a shop-vac for digging holes and that HEPA filters be used inside the shop-vac. Filters should be cleaned regularly by banging them, or blowing them off with compressed air whenever the airflow rate drops or upon dumping the container. Cyclonic filters such as Oneida’s Dust Deputy can significantly reduce the loading on shop-vac filters.
Soil Weight
Soil weight is an important criterion to consider when selecting a shop-vac for powering a Holey-Moley Digger. A one-foot deep hole will produce about 3 gallons of dirt that will weigh about 50 pounds. In many cases, a smaller shop-vacuum will work just fine. A five-gallon shop-vacuum is usually relatively easy to lift for dumping into a wheelbarrow. If you are digging a five-foot deep hole, you will produce roughly 15 gallons of dirt and it will weigh in at over 250 pounds. This starts pushing the structural integrity of most vacuums. If you intend to move the dirt to another location, a professional, contractor, or industrial model shop-vac will usually have large wheels on the rear with an appropriate handle for moving a full container.
Summary
When comparing shop-vac performance, do not use horsepower (hp) as criteria, as this is misleading. Look for the amperage or wattage, the higher the wattage or amperage the better. The single most important specification for comparison is the shop-vac airflow rating (CFM) which is an indication of how fast dirt will be removed from a hole. Hose diameter makes a big difference on dirt removal rate. If you have a choice, choose the vacuum with the larger hose diameter.
Typical hose diameters available on larger shop-vacuums are 2-inch and 2.5-inch. You will need at least 8-feet of hose for digging. Reducing the hose length by half can greatly increase the flow rate. Use a HEPA filter if one is available for the shop-vac you choose. When looking for a shop-vac for powering a Holey-Moley Digger consider professional, contractor, or industrial models. Look for the highest CFM, 2 to 2.5 inch hose diameter and hoses lengths in the 7 to 8 foot range.
Hole Digging Shop Vacuum – Some Comparisons
The following six shop-vacuums have good ratings, and reviews and should do very well digging holes and powering a Holey-Moley Digger. If the link does not work, do a copy paste into your browser.
Ridgid Model WD19650
This is one of the newer shop vacuums The Ridgid Model WD19560 on the market that we recently Comparison Tested with excellent results with air flow over 203 CFM. The vacuum proved to be one of the best vacuums used with the Holey-Moley Post Hole Digger.
Specification:
Wt – over 30 lbs
Amps – 12
General Warranty – 5 years Limited Household Use
Capacity – 16 gallon
CFM – 203
Tank – Stainless Steel
Voltage – 120
Hose Diameter – 2.5-inch (has ability to attach a 2-inch or 2.5-inch hose)
Hose length – 7 Feet
Blowing Port – Yes
Motor – ?
Shop-Vac Contractor Model 90L650A
The Shop-Vac Contractor Model 90L650A or equivalent is an excellent Hole Digging Shop Vacuum.
Note: The latest contractor model only pulls 150 CFM, this is the minimum we recommend.
no link available as this is an older model for comparison purposes only.
Specification:
Wt – over 30 lbs
Amps – 12
General Warranty – 5 years Limited Household Use
Capacity – 14 gallon
CFM – 180
Tank – Stainless Steel
Voltage – 120
Hose Diameter – 1.5-inch (has ability to attach a 2-inch or 2.5-inch hose)
Hose length – 12 Feet
Blowing Port – Yes
Motor – ?
Shop-vac 587-66-00
DISCONTINUED
The Shop-vac 587-66-00 is also a good Hole Digging Shop Vacuum. However, this vacuum has also been discontinued.
Note; Shop Vac went out of business and was bought by a China Company., This vacuum is very expensive and doesn’t have enough flow rate.
Specification:
Wt – ? lbs
Amps – 12
General Warranty – 3 years
Capacity – 16 gallon
CFM – 110
Tank – Stainless Steel
Voltage – 120
Hose Diameter – 1.5 inch
Hose length – 12 Feet
Blowing Port – Yes
Motor – ?
Static Suction – 72″
Peak Air Watts – 335
Vacmaster VJ1412P
The Vacmaster VJ1412P is an excellent Hole Digging Shop Vacuum.
Specification:
Wt –? lbs
Amps – 12
General Warranty – 3 years
Capacity – 14 gallon
CFM – 229
Tank – Plastic
Voltage – 120
Hose Diameter – 2-1/2 inch
Hose length – 10 Feet
Blowing Port – Yes
Motor – 2 stages
Static Suction – ?
Shop-Vac Contractor 32-Gallon 6.5-HP Wet/Dry Vac
DISCONTINUED
The Shop-Vac Contractor Model is a very good Hole Digging Shop-Vac.
Specification:
Wt – 45 lbs
Amps – 12
General Warranty – Limited Shop Lifetime
Capacity – 32 gallon
CFM – 195
Tank – Plastic
Voltage – 120
Hose Diameter – 1-1/2 inch
Hose length – 12 Feet
Blowing Port – ?
Motor – 2 stages
Static Suction – ?
Hole Digging Shop Vacuum
Tangential Gas Powered Vacuum Filter Bucket
One of the best Hole Digging Shop Vacuum systems on the market is the Makita Gasoline Powered Vacuum Filter Bucket by Cat 6 Tools.
This Makita Gasoline Powered Vacuum Filter Bucket System was developed by Cat 6 Tools, LLC specifically for dirt. Therefore it can pull gravel in at approximately 1/2 pound a second. A lot of good engineering went into this design, for instance, the system fits on top of a 7 gallon bucket and it has an easy on-off screw lid. The unit is powered by a high quality Makita 4-Cycle Gas Engine. The engine can run all day on one gallon of gas. What is especially relevant is this system works both as a blower and as a vacuum.
Light Weight
As a result of Cat 6 Tools excellent engineering, this unit weighs in at only 23 lbs this portable system is a perfect choice for the Holey-Moley Digger for digging holes where electricity is not available for running an electric shop vacuum. The light weight of the unit makes the system easy to carry on a back pack to remote areas.
Convertibility
And best of all the unique design of this system allows the Makita to be removed and easily converted back to a leaf blower. In addition, the tangential inlet of the bucket prevents clogging at the inlet if you run into damp soil. Above all the system comes with a standard Ridgid shop vacuum filter and there are 4 others to choose from. Even better, you can run this system with just the finger guard if your material is gravel, sand or moist dirt. Lots of options with this unit.
Specification:
Wt – 23 lbs
Uses Makita BHX2500CA blower
General Warranty – 1 year
Capacity – 7 gallon bucket
CFM – 230 with 8ft of vacuum hose.
Tank – Plastic
Hose Diameter – 2.1/2-inch
Hose length – 8 Feet
Blowing Port – Yes
Static Suction – 14.5″ H2O
Selecting the Best Hole Digging Shop Vacuum
Selecting the best Hole Digging Shop Vacuum comes down to a few simple criteria with airflow, CFM being the most important. Shop Vacuums with over 180 CFM are readily available with stainless steel tanks, large wheels to carry several hundred pounds, strong handles, 2 to 2.5 inch hoses, with good warranties. Contractor, Professional, and Industrial model shop vacuums usually fill all of these important criteria.
Some other links you may enjoy:
- Ridgid Shop Vac WD19560 Comparison Test
- Can Your Little Shop-Vac Suck Up Rocks?
- Digging Deep, Straight, Uniform Holes with a Shop-Vac
- Makita Vacuum Filter Bucket with Locking Ring Clamp