What Size Shop-Vac Do I Need?

A shop vac is a valuable tool to have around a house or business. Whether you expect to clean up small messes or large piles with chunks of debris, a shop vac can be indispensable in saving time and energy (when compared with sweeping). But the question is, how do you determine what size shop vac is best for you?

Shop vacs come in different sizes depending on what you need them for. The essential differences usually come in 5 categories:

• Tank size
• Hose size
• Sealed pressure
• CFM
• Horsepower

The sizes in each category are typically going to be rated light to heavy types of clean-up.

Knowing what you need your shop vac for will help you make sense of the categories. There is no point in getting a heavy-duty shop vac for a light-duty job. Throughout this article, the different categories of shop vac sizes will be discussed in terms of what they could be used to enable you to determine which size shop vac you need.

Common Shop-Vac Sizes

In general, shop vac sizes are typically structured around the kind of job they need to do. So it is a good idea to have in mind what constitutes light clean-up or heavy clean-up before you start rating vacuums according to those notions. That way, you will not end up buying a shop vac that is too large or small for what you need it for.

A small shop vac is going to be suited for light clean-up. If a box of crackers spills onto the floor, you will need a small shop vac for it. Or, if you want to vacuum up sawdust from a small woodworking project or a shop vac attachment to a portable sander to catch the dust, a small shop vac will do the trick.

A medium shop vac is going to be something you will need for larger projects. For example, if you tend to do a lot of home repair or improvement around your house, or if you need a wet-dry vac to clean up moderate spills or overflows, a medium shop vac is going to be the best choice for you.

Finally, a large shop vac is something you will need if you are engaged in major renovation projects around the home or if you are a professional contractor who regularly expects to clean up areas of heavy debris. You will also need a large shop vac if you expect to remove a lot of water over a large area.

Common Tank Sizes

Typically, shop vac tanks will be sized according to small, medium, and large ranges. As you may have guessed, you don’t need a large-sized tank for light, household clean-up, and a shop vac with a small tank is not going to go over well at a construction site. For this reason, the tank size often determines the overall size of the shop vac.

The ranges of size look like this:

• A small tank ranges between 2 and 6 gallons
• A medium tank ranges between 6 and 14 gallons
• A large tank ranges between 14 and 18 gallons

As you can see, large tanks are going to be best suited for large debris clean-up or water removal, while their size alone makes them not only unnecessary for small clean-up jobs but cumbersome. No one wants to muscle an 18 gallon shop vac through the house to clean up the oatmeal that spilled on the carpet.

Common Hose Sizes

Hose sizes tend to vary in terms of two measurements: diameter and length. Both variances tend to relate to shop vacs that are suited for small jobs versus big jobs. For example, you would expect a large shop vac to also have a hose with a large diameter for accommodating large pieces of debris.

Similarly, you would expect large shop vacs to have hoses that are longer in length. You want to be able to reach a larger area so that you move your large shop vac (which can be heavy and awkward to maneuver) as little as possible.

From small to large, diameter of hoses are typically:

•  27 mm
• One and ¼ inches
• One and ½ inches
• One and ⅞ inches
• Two and ½ inches

Typical lengths of hoses will vary from 7 to 12 feet. You can find couplers that allow you to link up hoses for a greater reach. But keep in mind that the longer the hose, the more your CFM decreases. So while you may be able to reach more, if you add too many lengths, you will ultimately be able to suck less.

Common Sealed Pressure Ratings

Sealed pressure (commonly called suction pressure) is how a shop vac is rated in terms of suction. Large shop vacs will typically have a higher sealed pressure rating, while small shop vacs will typically have a lower rating.

Suction pressure relates mostly to water removal. So it makes sense that your shop vacs with the highest sealed pressure are going to be at least medium sized and ideally large sized. You don’t want to have to remove a lot of water with only a 2 gallon tank. You would spend more time emptying the tank than sucking up the water.

Sealed pressure is determined based on how many inches a shop vac can suck water up a tube. It doesn’t sound very dramatic until you realize that a large heavy duty shop vac has a rating of around 70 to 75 inches. Over 75 inches is going to be a great rating for shop vac that is removing water. Smaller shop vacs will be rated around 50 inches.

Common CFM Sizes

CFM stands for “cubic feet per minute” and it measures the amount of air that goes through the vacuum’s largest opening. Shop vacs with a larger CFM are going to be able to pull more debris (and larger pieces of debris) into the hose than vacuums with a smaller CFM.

Shop vacs can have a wide range of CFM even within the small, medium, and large categories of shop vacs. Because small shop vacs tend to deal more with dust and light debris, they may have a high CFM.

Generally speaking, though, the three categories of shop vac sizes will have these ranges of CFM:

• Small size shop vacs will have between 60 and 75 CFM
• Medium size shop vacs will have between 75 and 150 CFM
• Large size shop vacs will have over 150 CFM

As you may have guessed, CFM, hose diameter, and tank size all tend to correlate. The higher the CFM, the more debris you can pull in, which means the hose diameter can be larger and the tank can be bigger to accommodate the debris.

Common Horsepower Sizes

Sometimes called peak horsepower, horsepower relates to the small, medium, and large shop vac sizes to the extent that it takes more horsepower to drive the higher CFM (or greater sealed pressure) to get larger debris (or water) through the bigger diameter hoses. In other words, the higher the horsepower, the larger the shop vac.

Horsepower tends to relate to shop vac sizes in this way:

• 1 to 4.5 horsepower motors run small shop vacs with a tank size of 2 to 6 gallons
• 5 to 6 horsepower motors run medium shop vacs with a tank size of 6 to 14 gallons
• Motors with a horsepower greater than 6 run large shop vacs with a tanks size of 14 to 18 gallons

As you might expect, the smaller horsepower motors are best suited for the clean-up of household debris. Medium horsepower motors can handle larger debris around the house in the garage. Some of these can also double as blowers. Finally, the large horsepower motors are best suited for professional heavy-duty use.

What is the Difference Between Suction and CFM?

In a little bit, this article will also answer the questions of which shop vac has the highest suction and which has the highest CFM. You may then wonder, what is the difference between suction and CFM? Maybe you thought one is as good as the other. But there is a difference, and understanding that will help you in selecting the right shop vac.

As we learned earlier, cubic feet per minute, or CFM, measures the amount of air that goes through the hose at its largest opening. CFM then is best related to what a shop vac can do in terms of taking in dust and debris. The higher the CFM, the more airflow goes through the hose and the more debris it can take with it.

Suction, or what we have called sealed pressure or suction pressure, relates to how much water the shop vac can pull through the hose. This may also be referred to as water lift. This measurement is in inches and describes how powerful a shop vac is in picking up spills or standing water.

Ideally you want a shop vac that has a balance of these measurements. For household applications, you will tend to see shop vacs with a higher CFM because the focus is going to be more on dust and debris than water. If you do pick up liquid, it will be from spills, not standing water.

Which Shop-Vac Has the Best Suction?

The shop vac which has the best suction is going to be the one with the highest sealed pressure or suction pressure. In order to qualify, the sealed pressure has to be greater than 75 inches.

There are a number of shop vacs which rank pretty high in this category. Here are a couple examples.

Fein Turbos I and II

The Fein company makes a line of shop vacs that are very impressive for their water lift capabilities. The I and II Turbo models both have a suction pressure of 98.4 inches. This makes these shop vacs a good choice if sucking up water is your biggest priority. There are a couple more things to consider about these models.

The Turbo I (link to Amazon) complements the high suction pressure with an admirable CFM of 151. It also has a long reach with a 13-foot vacuum hose and 19-foot power cord (source). Additionally, with its 18 pounds on swiveling casters, it is easy to maneuver. The Turbo I has a drawback in its 6-gallon tank. While not small, it is not as large as you may want.

The Turbo II (link to Amazon) is similar to the Turbo I in most respects, including an identical sealed pressure. It too has a CFM of 151 and similarly long reach with a 13-foot hose and an 18-foot cord. With swivel casters, it is significantly heavier at about 31 pounds. But the advantage of the Turbo II is that it has roughly an 8 and ½ gallon tank.

Dewalt 10 Gallon Portable Wet/Dry Shop Vac

The Dewalt 10 gallon wet/dry shop vac is a desirable item for a number of reasons, not the least of which is its ability to hold ten gallons of water. When you are faced with the removal of a lot of standing water, the 10-gallon tank could mean a few less trips to dump the tank, which in turn means more time spent removing water.

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But the other advantage is the sealed pressure of 80 inches that the shop vac delivers. This is a solid rating and gives the vac a distinct advantage in water removal. Unfortunately, the 5.5 horsepower motor does not balance the shop vac with a CFM higher than 90. That said, for suction, this is a good model.

Highest CFM Shop Vac

Just as some shop vacs have a high sealed pressure but may not be so great in the CFM department, some shop vacs are great in the CFM department but not so good at sealed pressure.

While ideally, you will want a balance of the two, if you find you have a greater need for debris and dust clean up, and if you like having the ability to do a blower conversion, then having a shop vac with a higher CFM might be a route to take. Here are a few to consider.

Ridgid WD1851

The Ridgid 16 gallon wet/dry shop vac is a beast with a high capacity for storing all the stuff you are trying to get rid of. It has an impressive CFM of 172. And while Rigid doesn’t list its sealed pressure rating, it does claim that the WD1851 can remove water at the rate of one gallon every second with a 6.5 horsepower motor (source).

The shop vac comes with a variety of nozzles that lock in place, which is a nice feature. Its 3 layer fine dust filter is a nice feature to go with the high capacity for sucking up debris. Having a good filter is essential for keeping the dust in the shop vac and not spreading it back to where it came from.

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With a cord length of 20 feet to add to the vacuum hose length, the Ridgid WD1851 weighs in at about 28 pounds, making it a hefty size, but not horrible when you consider how much the tank can hold.

Shop-Vac 4 Gallon Portable Wet/Dry Shop Vacuum

In this case, a shop vac is a brand, not just a kind of vacuum. But as it happens, it makes a stout little shop vac that has a clean, home-friendly design with a snazzy purple tank. At a four gallon capacity, this shop vac is definitely geared more toward home use, but is not lacking in the CFM department because of it.

In fact, it may be because of its home clean-up focus that the 4 horsepower motor conjures up a CFM of 170. At a nice 15 pounds, it is easy to tote around, but with an 18 foot long cord and 7 foot long hose, you may not have to.

Vacmaster Professional 10 Gallon Portable Wet/Dry Shop Vacuum

Vacmaster makes a shop vac with an impressive holding tank and nice CFM that sits right at 150. With a reach that extends to 28 feet with cord, hose, and wand, you can position this roughly 28 pound shop vac in the middle of your mess and commence with the clean-up.

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The Vacmaster has a 6.5 horsepower motor and a fine dust filter as well as a foam filter for wet applications (source). This makes the shop vac a solid tool, well-suited to clean-up from home projections and the like.

Conclusion

A shop vac can be an indispensable tool, even if you keep one around for clean up of household messes that sometimes get out of hand. But its use as a debris collector extends to projects and renovations. Being able to suck up dust, sawdust, and even loose nails and other construction debris is an invaluable aid to clean-up.

On the level of commercial use, having a powerful vacuum that can tackle heavy-duty debris and even standing water is a lifesaver. There are times when working with plumbing that accidents happen and water gets out of control. Bringing in a shop vac for immediate water removal can reduce damage to water-affected materials.

Related Reading:

Shop-Vac Blowing Stuff Out the Back: Possible Causes