I've tried to compile the most comprehensive guide to purchasing a wet/dry stop vacuum. Here you can learn about all of the characteristics of a wet/dry vac that you can search for on this site, and be fully informed so you can search for the perfect wet/dry shop vac to meet your needs.
Below are explanations of each of the characteristics of these vacuums that are searchable on this site.
There are a number of brands of wet/dry shop vacuums today. While a few brands are actually manufactured by the company that is presented to you, most wet/dry vacuum brands are actually manufactured by different companies—mostly in China, that you probably have never heard of. There are several manufacturers who make multiple brands of vacuums, and sometimes even sell the exact same vacuum at different prices under different brand names. So, avoid the temptation to confuse brand and manufacturer. For the most part, most manufacturers try to obscure their connection with which brands they produce. This site digs deep to reveal who makes what.
For instance, Alton Industries makes all Stanley and most Porter-Cable and Dewalt wet/dry vacuums! They also have their own brand called STEALTH. Understanding these relationships can be important for your vacuum choice. You might love how Dewalt manufacturers its drills, but that would not be a reason to purchase a large Dewalt vaccuum, since it's not manufactured by them—Dewalt licensed their brand name for vacuums to Alton Industries.
Perhaps you are looking at getting a 1.5 gallon Armor All vacuum. Knowing that both Armor All and Vacmaster are manufactured by Cleva, you might then take a look at the less expensive Vacmaster model that's the same size with the same HP motor—and is in fact, the exact same vacuum. Nope, Armor All vacuums are not actually made by the same company that makes the spray-on protector for the vinyl in your car.
The relationship between brand and manufacturer is far more complicated than you would probably ever guess. For instance, DeWALT brand 120-volt vacuums are manufactured by Alton Industry, which licenses the DeWALT brand name for vacuums. DeWALT brand smaller battery-powered vacuums are actually manufactured by the DeWALT company. The DeWALT company is now a subsidiary of Stanley Black & Decker. Stanley Black & Decker manufactures CRAFTSMAN vacuums. There are also Stanley brand vacuums—those are manufactured by Alton Industry, who licensed the Stanley name for vacuums before Stanley and Black & Decker merged in 2010! Fortunately, this site makes sense of it all for you.
Vacuums within a brand usually share a common look, including color scheme, and typically use the same filters between different models of similiar sizes. Larger brands like Shop-Vac® and Vacmaster have multiple branded series of vacuums, each of which have a similiar look, function, and features.
You can see the current List of All Wet/Dry Vac Brands that are on this site, and view a detailed Brand page for each of them, which is also accessible from the Vacuum detail page if you click on the name of the brand.
This is who actually makes the vacuum. There are fewer manufacturers than there are brands. It's common for different brands produced by the same manufacturer to share the same motors and other components, and just be styled and colored diffently to represent the various brands.
Most wet/dry vacuums are manufactured in China nowadays. The largest and original US manufacturer, the privately held Shop-Vac company, went out of business in 2020, and the brand now belongs to a chinese company—Hangzhou GreatStar Industrial Co., Ltd. In the case of a large company where the vacuum is manufactured by a subsidiary (or two), I will list the name of the parent company.
Model number. For some brands, model numbers are meaningful, telling you which line of vacuum each model is a part of or what sort of motor or capacity it has. For other brands, it seems to be more or less just random numbers. There are also some particular vacuums that appear to have multiple model numbers even though they are the same vacuum. This is to usually to accomodate retailers that have "price match" or lowest price guarantees. It's the same gimmick used by mattress makers and others—if nobody else carries the same model number, then you will always have the lowest price on it. I've tried to combine such models into a single entry on this site.
In all cases where there is both a model number and in item or catalog number for each vacuum, the model number is presented first, and the item or catalog number is listed afterwards in parenthesis.
Shop-Vac, for instance, always had two identifiers for each vacuum--a "model number" that was alphanumeric, and an "item number" that was a number—sort of a catalog number. After Shop-Vac closed and the brand was purchased by Hangzhou GreatStar Industrial Co., Ltd. in China, they went back to manufacturing the vacuums with the same item numbers but DIFFERENT model numbers. And, unfortunately the new model numbers have no meaning other than when they started making them, so you can no longer know anything about the type of vacuum from their model numbers.
The majority of these vacuums have tanks that are made of plastic, typically polypropylene. Some, however, are made with stainless steel or occassionally other metals. For most purposes, plastic tanks are the most practical. They are fairly light, don't dent, don't rust, and are not affected by most acids or corrosive compounds. There are certain cases, however, where a metal tank might be preferable. For instance, if you are vacumming hot materials like ash, which could potentially melt or ignite a plastic tank.
Capacity is typically measured in gallons, but there's a catch. It refers to the capacity of the tank of the vacuum cleaner, if you were to fill it to the top. Of course, there's a filter that has to be in there too, as well as some air space beneath the filter. So the actual capacity of how much debris you can hold in the vacuum is substantially less.
Generally, larger vacuums are also more powerful, but they are also usually heavier, bulkier, and more expensive. For most people wanting a general purpose vac, the medium sizes work best, between 4 and 12 gallons.
This is the number of sets of fan blades in a vacuum motor. Each set of blades increases the vacuum, or speed at which air is pulled through. A two-stage motor is able to provide a stronger vacuum at the same rotation speed versus a single-stage motor. Or, it can provide the same amount of vacuum as a single-stage motor while rotating more slowly. This allows it to be quieter, more efficient, and to have a longer service life than a single-stage motor.
Weight in pounds: Heavier vacuums are harder to move around, but they might be heavier because they are more solidy built.
Volts, Amps, and Watts are all provided, since manufacturers tend to list only amps or only watts. Missing specifications are calculated here (watts = volts * amps)
For the same quality and type of motor, higher amperage or wattage (using more electricity) should mean more power, but a higher quality motor will require less electricity for a given power output.
The maximum instantaneous horsepower of the motor on startup. While this is the most commonly used comparison attribute, it's fairly useless. The maximum running horsepower of most vacuums is nowhere near to this, and higher quality industrial motors will have a lower peak horsepower rating than low quality ones, while actualy having higher output.
Cubic feet per minute of air. This is the maximum amout of air that can be moved by a vacuum motor at no load (no lift). Longer hoses, accessory tools, or a dirty filter will reduce this flow, as will picking up anything with the vacuum.
Lift, or Sealed Pressure (SP), is the maximum inches up a tube a vacuum motor will lift a column of water. At this maximim point, air flow (CFM) is zero. Lift decreases as air flow (CFM) increases. In metric, this is represented as Kilopascals, where 1 Kilopascal is equal to 4.01865 inches of water.
A standardized way of representing the maximum air power available at a nozzle. It is calculated as:
Air Watts = Lift * CFM/8.5
Noise level (sound pressure) in decibels. Wet/Dry vacuums are notorious for being loud. Two-stage motors don't need to turn as fast, so they are generally quieter. Some vacuums have air/noise diffusers which also help, though they can slightly reduce performance. It's generally best to get a quieter vacuum for general use, unless you'll already be wearing hearing protection and it really doesn't matter.
Unfortunately, many manufacturers don't publish dB for their vacuums. The models that are published tend to be the quieter ones. I spoke with the Shop-Vac company in 2019 to ask about decibel ratings, and they said that they stopped publishing those about 4 years ago because of their competitors publishing lower dB numbers, insinuating that they were falsifying their tests. It's hard to know what the truth is here--that could well be true, or it could be that most Shop-Vac models were just louder. It's a shame that data like that is not readily available for most models.
Power cord length in feet: Generally (within reason), if you are moving the vacuum around, a longer cord is better, so that you avoid having to use an extension cord. However, a longer cord means more to coil up to put away. If you are looking for a fixed, wall-mounted vacuum, then you just need a cord that reaches to the nearest outlet.
Another issue, however, is that most of these vacuums draw a lot of current (amperage), and most manufacturers use wires as thin as possible to save money (copper is very expensive). Many use 18-guage (18AWG) wire, which is barely thick enough, so that it will typically heat up with use. The longer the wire, the larger (lower gauge) it should be, as there is more power loss (as heat from resistance) over the length of the wire. Some higher quality vacuums use as large as 14AWG wire. It's always better if you can get a vacuum with a lower-gauge (thicker) power cord—I would try to get 16AWG or lower when possible. I've tried to note wire gauges as I can find them in the notes for each vacuum.
Hose diameter in inches: Thicker hoses will provide better suction for a given vacuum, and will be less likely to get clogged with large debris. However, it's a lot bulkier to store and to maneuver. Hoses range in size from 1" to 2.5" diameter, with the larger and more powerful vacuums typically having higher diameter hoses.
Hose length in feet: Longer hoses are often more convenient for vacuuming, but less convenient to coil up and put away. Also, the longer the hose for a given vacuum, the less suction you'll get.
This is the maximum number of years that any warranty is valid, though sometimes they are quite 'limited'. Some manufacturers have longer warranties on the motor than the rest of the vacuum. Others have lifetime warranties against manufacturing defects, but if your motor wears out in a year you might be out of luck.
Most wet/dry vacuums come with wheels of some sort, unless they are intended to be wall mounted, or else are fairly small vacuums that are easy enough to carry. Most of the time, vacs have casters, but sometimes they are attached to a dolly with larger wheels.
Ones with all casters are more maneuverable as they can easily turn in any direction. These are best for use on hard, level relatively even surfaces. However casters are small and are not good if you have to move the vacuum over very rough surfaces, or wheel it across a lawn to dump it, etc.
Ones that have fixed larger wheels (usually two, and the other two are smaller wheels or casters), are a bit harder to drag around on flat surfaces, since the wheels don't change direction as easily. But they are much easiest to drag over uneven terrain. Some are essentially setup as dollies that the vacuum is mounted on, so that they can be moved around like a hand truck.
No one type is better or worse—it all depends on how you'll be using it. Within each type, of course, there are lots of quality difference. Metal ball-bearing casters will certainly work a lot more smoothly than cheap flimsy plastic ones.
Vacuums that are wall-mountable come with brackets for mounting on the wall. There two classes of wall-mountable vacuums. One type are smaller vacuums with short hoses that are meant to be carried when used, which include brackets to mount on the wall for storage when not in use. The other type are vacuums that are meant to stay on the wall during use to become a sort of centralized vacuum for a space. These have long, often VERY long hoses, and are intented to be mounted in a gararage, workshop, basement or similiar location such that the hose can reach the floors or vehicles that you need to vacuum. These still tend to be small to medium-sized vacuume, since it would become too cumbersome to take down a very large vacuum from the wall to empty the tank or change the filter bags.
Many vacs, especially larger ones with wheels, have drains so that you empty liquid out without having to lift the vacuum tank. On smaller or wall-mounted units, it makes far less sense to have a drain. Generally, this is just a drain plug that you can remove to allow the fluid to drain out. Some models have standard garden hose size connectors for drainage, while some other more specialized vacs include actually pumps to pump the fluid out.
Some vacs have a blower featuer. Usually this is just the ability to connect the vacuum hose to the exhaust port of the unit. This can be useful for cleanup where you can't reach to vacuum debris—you can can blow it away. This can also be useful for blowing leaves, but a machine designed as a vacuum will never be as powerful as a dedicated leaf blower. There are a few models that have detachable heads to use for blowing, so that you don't need to carry the tank around with you.
Are washable filters available for this vacuum? Having washable (really should be called rinseable) filters can save you a lot of money versus non-washable ones, especially if you often vacuum up fine particles that will clog a filter, or damp debris that will stick to it. Sometimes "washable" is not a clear-cut term to use. Some filters are super-durable and you can spray them off with a hose over and over again and be fine. Other can be very gently rinsed without pressure a few times and still used. Both of these types I am classifying as "washable". Some other filters simply can never get wet at all, and as soon as they do, the paper that they are made of will fall apart.
In all cases where you can rinse a filter, you must allow it to fully dry before using it again, or it will not work and you will destroy it. If you are planning on doing that, I would strongly suggest that you make sure you have an extra filter on hand. That way, you can take one out an rinse it, set it aside to slowly dry, and put your dry filter into your vacuum so that it's ready to use again.
Most wet/dry vacuums come with, or will work with, foam filters. These are always washable, but they are intended for vacuuming liquids, and would do little to filter any particles out of the air. Mostly they just protect the motor from spinning too fast and from getting dirty liquids spashed into the fan blades.
Some vacs either come with HEPA filters installed or offer HEPA filters that can be used with the unit. HEPA is an acronym for "High Efficiency Particulate Air" and is defined to be a filter that removes at least 99.97% of particles that have a size greater or equal to 0.3 micrometers (microns). Vacuums with these very fine filters installed will not blow dust into the air. This is particularly useful for very fine dust that can be harmful, like asbestos or mold spores, or if you are cleaning a space where allergies to dust, pollen, or pet dander are an issue. These filters are usually (but not always) more expensive than courser filters.