There are times when you face special cleaning needs which your household vacuum cleaner just isn't designed to handle. These include picking up water or large particles of dirt or debris. The wet/dry utility vacuum, alias shop-vac, comes to the rescue with its special capabilities. This breed of vacuum cleaner has been around for many years, often setting in a corner of the basement or shop waiting for those times of special need. One company, Shop-Vac Corporation, even uses the alias for the wet/dry utility vacuum as part of its name. They probably are the longest continuous manufacturer of this type of vacuum cleaner although a number of other companies also manufacture these useful machines.
Uniquely Designed for Water Pickup
As mentioned earlier, one of the special uses of these machines is to pick up water, something few household vacuum cleaners can do. Special design characteristics are built in so that large volumes of water can be accommodated without damage to the entire unit. Most canister type household vacuums use a suction motor which is cooled by the same air which picks up the dirt. Since the air which picked up the water contains large amounts of moisture, the wet/dry utility vacuum exhausts the air after it passes through the suction creating fan and uses a separate fan to circulate clean air around the armature and field to cool them. A motor using this basic design which is also used by its bigger brother, the industrial vacuum, is know as a bypass cooled motor. For more information about the various types of motors used in vacuum cleaners, see our article on Suction Motor Design & Operation.
Another design feature to enable safe water pickup is the shutoff valve which is designed into the housing just below the motor intake. This is typically a ball or cylinder shaped float which, when the maximum water capacity is reached, moves upward against a seal to stop the air flow. The user notices the different sound of the motor, turns it off and empties the tank. Some newer units contain a very convenient capped drain at the bottom of the tank for much easier and more controlled emptying of the water. This can eliminate the need to lift or tilt a very heavy water filled tank.
Cleaning Large Particles
Besides being used for water pickup, the wet/dry utility vacuum is often used to clean either large amounts or large particles of dry dirt. A wood shop or home construction and remodeling often creates large amounts of debris which is too large to pass through a household vacuum's 1 1/4" hose without frequent clogging. Utility vacuums typically have 2 1/4" hose inlets which will accommodate extra large diameter 2 1/4" hoses, the 1 1/2" commercial size hoses or the 1 1/4" household size hoses.
Various Hose Sizes and Their Benefits
The extra large 2 1/4" hose is recommended when it will be used to pick up large particles but due to its large size, it is often hard to handle when cleaning smaller areas like the interior of a car or truck or when working around equipment. Another drawback is caused by the large cross area of the hose as well as its ability to be stretched. When the user restricts the air flow by placing the nozzle against the surface being cleaned, the large amount of force created by the suction acting upon the large cross area tries to pull the hose end toward the vacuum, fighting the efforts of the user to stretch the hose. Sometimes this can be enough force to actually tip some utility vacuums over on their sides.
Another common hose size used on wet/dry utility vacuums is the 1 1/4" household size hose. This is typically a six foot, non-stretch hose which is very nice for many smaller jobs around the house or small shop. It is much easier to handle than the extra large size and will accommodate most small attachments used on household vacuums. The end which attaches to the unit adapts it to the large 2 1/4" hose inlet. See our page of Wet/Dry Accessories for 2 1/4" and 1 1/4" attachments.
For longer reaches and tougher uses, the ten foot long 1 1/2" commercial size hose is the most ideal. Its larger diameter permits good air flow with very little internal resistance so it is good for those longer reaches. Its construction is more commercial quality as well so durability should be excellent. It handles almost as easily as the small household size hose. Adapters are available to use 1 1/4" household attachments on this and other commercial hoses. Some wet/dry utility vacuum cleaners like the Shop-Vac Contractor 610 series even include the larger 1 1/2" attachments for those heavy duty jobs. See our page of 1 1/2" Diameter Accessories to fit Most Commercial Canister Vacuums for these commercial type attachments.
Filtration Considerations
Large volumes of dirt would quickly fill most household vacuum cleaner paper bags but are handled efficiently by the large capacity of most wet/dry utility vacuums. The dirt goes directly into the large tank which can be easily emptied when full, saving the cost of disposable paper bags. The filter is mounted just below the motor inlet, often surrounding the water shutoff valve. Most units come with two different types of filters, a foam one for use when picking up water and a corrugated type filter cartridge for picking up dry dirt and debris. Some use a simple paper or fabric type filter which fits directly over the foam one for dry pickup but the limited filter area significantly reduces the air flow and performance as dust accumulates on it. The corrugated (fan-fold) filter secured in a cartridge provides a much greater surface area so the actual resistance to the air flow is much less as dust accumulates on it.
Summary
One final word about the abilities of most wet/dry utility vacuums. You may be tempted to use one of these units to do you regular household cleaning instead of using a vacuum cleaner designed for that task. While these units are designed to do some special tasks like water pickup, cleaning large size dirt and debris and blowing grass and leaves, they typically are not as powerful nor filter as well as most household type vacuum cleaners. The wet/dry utility vac is a specialty type of vacuum cleaner which does what it is designed to do very well. Likewise, the household vacuum cleaner is designed to clean you house very well week after week, year after year. Each has its own arena where it will perform well, easing your cleaning work load for years to come.
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