There is a lot of information about digging cache tube holes, post holes, and digging in general in the following Holey-Moley Digger FAQ.  If you have additional questions give us a call, we are here to help.  We will continue to post additional information in this FAQ post. For additional information you can print click on the Holey-Moley mini brochure pdf.

Holey-Moley Digger Helpline – 702-533-4363

How deep of a hole can be dug with the Holey-Moley Digger?

A common FAQ asks about hole depth.  A reasonable limit to hole depth is around 18 to 20 feet. At this depth, it may take two persons to lift the digger out of the hole. Nineteen feet is the length of a section of pipe with the bell end cut off. The length and weight makes lifting the entire assembly out of a hole a bit cumbersome. To dig a 20-foot deep hole, would require a 19-foot piece of  pipe and a 3-foot extension for 22 total feet.   A 20-foot long digger would weigh a bit over 50 pounds. Ten to 15 foot holes are well within the operating range of the digger. For holes 10 to 20 feet deep, it is recommended that a shop vacuum with at least 200 CFM flow rate be used with a 2-1/2 inch hose.  To make the process of lifting the digger out of the ground, lifting handle holes can be added


Other than what comes in a kit, what do I need to buy?

Kits do not come with Pipe (6-inch and 2-inch), or a Shop Vacuum. We do not carry pipe because the cost of shipping pipe usually exceeds the price of the pipe and it is readily available from local suppliers. Shop vacuums are also readily available from local hardware companies or large on-line suppliers. See our pages on What you need – Pipe & Materials and What you need – Tools & Shop Vacuum.

If you are buying a Holey-Moley Digger kit, assembled or unassembled, you will need 6-inch PVC D3034 (green) sewer pipe (white pipe can also work, however it is more expensive) and 2-inch PVC water pipe of any wall thickness. Your piple will be cut to length to match your digging situation. The kits have sample pieces of pipe that you can take to your supplier so they will know what you need. You can also take a coupling from the kit to make sure the pipe you are buying fits.

You will also need a shop vacuum that provides upwards of 180 to 200 CFM. Try your own shop vacuum first if you have one.   See our section on what you need for pipe and shop vacuum for detailed information.


Do I need to call 811 before I dig a hole?

811 is a new national “Call Before You Dig” number designated by the FCC to help protect homeowners and professional excavators from injuries, expenses and penalties. This new national safety resource will make it easy for homeowners and professionals across the country to protect themselves by calling before beginning any digging project, whether it be something small like planting a tree or installing a mailbox or a larger project like building an addition or deck. Remember to call 811 before you have a problem and need to call 911. For more information go to call811.com.  We will post additional important information in our blog and here in FAQ section.


What is the specification for the digger’s 6-inch pipe?

The Holey-Moley Digger backbone pipe is standard SDR 35, ASTM D3034 Gravity Sewer Pipe – Green Color. The OD of the Pipe is 6.275 inches. The ID of the pipe is 5.915 inches. The pipe wall thickness classification is SDR 35, is .180 inches. The weight per foot is 2.4362 lbs. The pipe comes in 14 foot and 20 foot lengths.
Here is a link to North American Pipe’s specification sheet for D3034 pipe.


Here is a link to Cresline-Nortwest’s information sheet on sewer pipe: http://www.cresline.com/pdf/cresline-northwest/pvcds%26sewerpipe/CNWPVC-353034GJ.pdf


What is the specification for the digger’s 6-inch Solvent Weld Coupling?

The couplings are 6.25 inches long. The inside rib is .25 inches thick. Pipe insert distance is 3.0 inches. The width of coupling is 6.75 inches at the widest end and approximately 1/16 inch smaller on the opposite end. This is because the coupling needs to be tapered to come out of its mold.


What is the actual diameter of the hole the Holey-Moley digs?

The outside of diameter of the coupling is 6.75 inches. The saw blade is 16-gage mild steel, which is .0598 inches thick. The total diameter is approximately 6.87 inches. When digging, the digger actually produces a hole approximately 7 inches in diameter.


What is the actual diameter of the hole the reamer produces?

The reamer blades extend out from the digger pipe approximately 1.0 inches. This adds 2-inches to the diameter of the D3034 sewer pipe that the blades are mounted on which is 6.275 inches. The total diameter of the reamed hole is approximately 8.275 inches. In practice, the reamer produces a hole slightly larger to about 8.5 to 9-inches in diameter. This is large enough to insert an 8-inch Sewer Pipe for a casing that has an OD of 8.40 inches.


Does the Digger pipe, digger head, and digger handle, or the vacuum pipe need to be glued together?

No, in most cases the slip fit resistance is enough to dig most holes. For holes that are over 5 feet deep, one might want to use two rivets, 180 degrees apart, to attach the digger head to the 6-inch pipe, these can be drilled and riveted about 1.5 inches from the end of the coupling and through the coupling and the green pipe. Do the same for the handle coupling. For the connecting coupling for deeper holes, secure the coupling to the top and the lower sections of pipe with two rivets on each end of the coupling (the top and bottom) for the respective pipe lengths, four rivets total. These rivets will be more than enough to prevent the joints from coming apart. The rivets can be drilled out easily with a 1/8-inch drill to remove them. The 2-inch PVC suction pipe does not require any glue or rivets, as there is no force being applied. This also allows for the suction pipe and couplings to be easily assembled and disassembled.


If I have a smaller shop vacuum, do I need to buy a new one?

As a rule of thumb, try your shop vacuum first. This will give you a good feel for what you might need. We have tested an old, 5-gallon Dayton shop vacuum rated at 6 amps and it worked just as well as a 14 gallon 12 amp shop vacuum. The real key to digging is to use the largest diameter hose, typically 2.5 to 3.0-inches in diameter, and use a clean filter. One good test is to use your shop vacuum to vacuum up 5-gallons of sand and gravel. You should be able to empty the 5-gallon bucket in less than 2 minutes using 4 feet of 2.5 to 3.0-inch hose. With the same hose diameter, 12 feet long, the time to pick up 5-gallons of sand and gravel will go out to 10 or 12 minutes. This would still be adequate for digging.  Hose kits are available at most hardware stores.  See other FAQ for additional information.


Will the Holey-Moley Digger dig in wet ground?

The digger works best in dry ground. Moisture binds the dirt particles together and they are difficult to lift with air. When the soil moisture is 10% moisture content or below, the digger works well. The high airflow rate of the digger will dry out moist dirt to some degree. With moist clay soils, the uptake soil may cake and dry hard onto the blades and to the diverter plate found in some shop vacuums at the inlet. An inexpensive moisture meter for potted plants, which you can find at most hardware stores, is very good for determining the moisture content of the soil. In our testing, we have tried dug holes in high moisture clay where we had to lift the digger and clean the blades regularly with a high-pressure water hose. We were able to dig a hole in what seemed to be quite an un-conventional manner, using the digger to pick up the accumulated clay and the shop vac hose was used to pick up gravel and moist clay after we lifted the digger out. The sides of the hole dried out rapidly to be almost like concrete within minutes. After several feet of digging in this manner better soil was penetrated and the digging rate significantly increased.  This shows some creative ways of using the digger.


How big of a rock, will the digger lift up?

The digger is intentionally designed to be self-limiting on the size of rock that will be sucked into the suction line. Stones up to 1-1/2 inch can be sucked up depending on the shop vacuum flow rate. The main impediment of the digger are stones that larger than 2-inches in diameter. Stones will accumulate in the bottom of the hole and help in pulverizing the soil for uptake. When the digging penetrating rate drops off, or when the digger is hard to rotate, it should be pulled out of the hole and the suction hose put directly down the hole to pick up loose rocks. In our testing we have pulled rocks as big as 3 to 4-inches out of holes using the shop vacuum hose. The filter should be cleaned before fishing stones out of the hole to get the highest flow rate through the hose. A two-inch line pulling 80% vacuum at sea level can lift close to 30 lbs. A slightly flexible hose end that can adapt to the contour of the rocks can pull most stones out of a hole.  The photo below shows gravel that was pulled up through the digger vacuum line.

Gravel picked up with the Holey-Moley Digger


What is the digging rate of the Holey-Moley Digger?

The amount of gravel and dirt that is lifted by the digger is dependent on the shop vacuum, the vacuum hose diameter, the airflow rate, as well as the type of soil and the moisture in the soil. When digging some holes you may hit a big rock and the only option is to move the hole to a different location. Tests that we have done show that in loose, dry soils that are mixed with small gravel, the uptake rate can be on the order of 5 gallons every 10 to 15 minutes.


How does soil moisture content affect digging with the Holey-Moley Digger?

Soil moisture is one of the biggest factors influencing digging rates, and when it gets to over 10%, the binding of the soil particles makes it nearly impossible to move them with air. Sometimes this is just a surface issue and once a hole is down a foot or two, the digger then works well. We have had the opportunity to work in hard packed clay mixed with sand in different seasons. In wet seasons, we cannot dig at all, in dry seasons the digger works well and it worked even better with a small amount of moisture just like you would expect if you were to dig a hole with a pick and shovel. Moisture affects the digger the same way.  A potted plant moisture meter, available at most hardware stores or nurseries, works well for determining the moisture content of soil.


Will the digger cut through tree roots?

The digger will cut through small roots. When roots are encountered, pull the digger out of the hole and remove the roots that accumulate, as they will not go through the suction pipe. Large roots may take a bit more effort. Roots that are over several inches will be difficult and may require other tools to cut. Sometimes it is easier to move to another location. In the photo below, the digger saw blade easily cut through the 1.5-inch horizontal root on the left but was unable to cut through the same root that transitioned to vertical at the bottom of the hole.   An attempt was made to cut the root apart but moving several feet to a new location was much easier.  See other FAQ for further information.


The Holey-Moley Digger can cut through tree roots


Will the digger work in caliche?

The Holy-Moley Digger, as robust a digging tool as it is will not work in caliche. The term caliche is usually used to refer to soils that are cement in nature, contain hard stones and rocks that vary in size, from gravels to boulders, and require considerable mechanical effort to penetrate. Penetration may require jackhammers, rotary drills, or tractor mounted augers.  The digger will penetrate hardpan and hard clays with gravel as shown below.

6-Inch hole dug with Holey-Moley Digger in Hard Pan & Clay


  • Caliche – is defined as a mineral deposit of gravel, sand, and nitrates, found especially in dry areas of South America. It is also defined as an area of calcium carbonate or other carbonates formed in the soils of semiarid regions. Caliche is also referred to as a surface deposit consisting of sand or clay impregnated with crystalline salts such as sodium nitrate or sodium chloride.



  • Duricrust – is defined as a hard crust that forms on or in soil in semiarid climates owing to cementation of soil particles. Duricrust is also referred to as a hard mineral crust formed at or near the surface of soil in semiarid regions by the evaporation of groundwater. Duricrust also refers to a hard layer on or near the surface of soil. Duricrusts can range in thickness from a few millimeters or centimeters to several meters. It is a general term (not to be confused with Duripan) for a zone of chemical precipitation and hardening formed at or near the surface of sedimentary bodies.
  • Durapan – also occur in arid or semiarid climates, where the soil is usually dry or seasonally dry and are often geographically associated with areas of volcanic activity, and show evidence of ash or volcanic glass deposition. Volcanic glass weathers rapidly, providing an ample supply of soluble silica to cement the underlying soil.


Are there any parameters that I can control to optimize digging with a shop-vacuum?

Yes. There are several that you have control over. The most important is to minimize the hose length from the shop-vacuum and the second is to use the largest diameter hose possible. We strongly suggest that you use a 2.5-inch to 3-inch hose if possible.   The second area to pay attention to is the cleanliness of your shop-vac filter. If you bang it good to knock off accumulated dirt about every 3 to 5 gallons or when the digging rate slows down, you will see a dramatic increase in flow rate as high as 10% to 20%. Usually you can hear the debris flowing through the hose. When this slows down, you might want to check the filter or see if you have some clogging of your hose, usually at the vacuum inlet. One of the least controllable parameters is moisture.   If the ground is above a 10% moisture content, you will see an accumulation of soil in the digger head around the scraper blades and at the vacuum inlet. If the soil has some clay content, these accumulations will dry out very fast and become very hard. Periodically you can lift the digger 6 or 8-inches and bang on the digger pipe with a mallet and this will help to knock off some of the accumulation at the digger head. One or two good whacks will do it.  If the digger head is gummed up pretty well, you can always wash it out with a hose.  More information can be found in other FAQ posted here.


Is there anything I can do to get through damp ground? 

There are pros and cons to damp ground. With a bit of clay in the soil, the side walls of the hole will dry out relatively fast and will become extremely hard. This is like having a concrete casing in place.   The cons are that the digger head will clog up relatively fast.   You will have to pull the digger out of the ground and clean up the blades. This can be as easy as using a screw driver or giving the digger head a whack with a mallet. If the soil is of high clay content, you may have to use a hose to periodically wash out the digger head and even the vacuum hose. Normally this sort of condition exists for several feet and transitions into more manageable ground.  Sometimes, removing the digger and blowing shop vac exhaust air through the hose into the bottom of the hole will help dry the soil out.


What is your warranty and return policy?

Our manufactured products carry a 1-year warranty for workmanship and quality. Should any of parts fail during the first year from general use and not abused by digging rocks or materials that will damage the materials. Generally, we have a 30-day return policy. For kits, if they are assembled (holes drilled and parts riveted together) we will not accept a return. We will not accept returns on products that are used. If you dig a hole with the digger, it is considered non-returnable.  If you are having trouble, give us a call.  We want our customers to be happy.  See our Return Policy more specifics.


What is return policy?

Yes, our standard policy is 30 days, complete return if unopened. If the product is opened, there will be a restocking fee. In all cases, the customer pays for shipping costs. If shipping is free to the customer, the customer will be charged for the shipping fee to them. Items that Holey-Moley represents, such as the Portable Engine Driven Vacuum, will fall under the return policy of the manufacturer, and returns will be to them.


Do I pay for shipping?

Our policy for for most items will be shipped the cheapest way, usually by UPS. In some cases, shipping will be by USPS. Special shipping rates will apply if by other than standard shipping. For special or faster shipping customers should contact Holey-Moley directly, by email, or by phone.

We are continually looking for product reviewers.  If you are a product reviewer and interested in using our products we would like to talk with you.

We hope you have enjoyed our postings in this FAQ section.   If you have any questions not covered here please give us a call or send an email.  We will be happy to respond.  We are interested in your digging experiences and will add good tips to our FAQ post.