How to Use a Shop Vac for Water

a shop vacuum sitting on the garage floor
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Project Overview
  • Working Time: 15 - 30 mins
  • Total Time: 15 - 30 mins
  • Yield: 10 square-foot area
  • Skill Level: Beginner
  • Estimated Cost: $75 to $150

A wet/dry shop vacuum is indispensable around the home. Despite the name, a shop vacuum's utility extends far beyond the workshop since it tackles messes that ordinary household vacuums cannot handle.

A shop vacuum's ability to suck up water saves you from using towels to soak up water on the floor or trying to squeegee it away. A shop vacuum even acts as a pump to remove larger quantities of water standing in a tub, shower, pool, aquarium, or garden pond.

How a Shop Vacuum Removes Water

A vacuum is perfectly named because this describes its inner workings. At the top of every shop vacuum is an electric motor that turns a fan. This fan sucks the air out of the shop vacuum's large lower container or basin, creating that condition you learned about in physics class: a vacuum.

If this were a closed container, the container would eventually suck inward or implode. But a shop vacuum has a hole near the top to permit replacement air to enter the container. When a hose is attached to this hole, dirt and debris can be sucked into the container. Can the hose be applied to water instead of dry items?

It works much the same way, with a couple of differences. For one, all dry-use filters on the shop vacuum must be removed. With most models, this includes the paper bag and paper filter but not the foam filter. Paper filters become water-logged, impeding airflow.

For another—and most importantly—the water cannot be allowed to rise as high as the motor and fan. The vacuum will begin to bog down enough that this will not happen purely due to the vacuum. But user error may cause this. It's possible to move the vacuum around so vigorously that water sloshes up into the motor and fan area.

What's the Best Type of Wet/Dry Vacuum to Buy?

Wet/dry vacuums range in capacity from 1 gallon up to 20 gallons, with most vacuums in the 4- to 10-gallon capacity range.

A few inches of water in a tub or water spread out across a wide area will quickly fill up smaller vacuums. The amount of water in carpeting is difficult to estimate because the water is not visible. With water soaking into the fibers and the padding, carpeting can hold as much as 1 gallon per square foot.

If you want to vacuum up large quantities of water, a higher capacity wet/dry vacuum is helpful to avoid frequently pouring out the canister. At the same time, large canisters full of water are heavy and unwieldy. With water weighing close to 8 1/2 pounds per gallon, full wet/dry vacuums on the higher end of the moderate capacity range weigh as much as 130 pounds.

An Overview of Using a Wet/Dry Vacuum With Water

  • Estimate amount of water
  • Plug into a GFCI outlet
  • Remove bag
  • Remove dry filter (wet filters are fine)
  • Be aware of the quantity of water in the canister
  • Dispose of water properly
  • Clean and dry canister and accessories

Safety Considerations

Use only on a grounded GFCI outlet. Use a three-prong extension cord that is rated for the shop vacuum's amperage.

What You'll Need

Equipment / Tools

  • 1 Wet/Dry Vacuum

Materials

  • Wet filter

Instructions

  1. Remove Bag

    During wet operation, wet/dry vacuums never use collection bags. Unlatch the top, blower-unit section of the vacuum. Remove the collection bag and any fasteners and set it aside.

  2. Change or Remove Filters

    Since they are made of paper, dry filters are never used during wet operation. In some cases, they are plastic units with attached pleated paper folds. Or they might be filter cloths that wrap around the filter unit, secured with a rubber band. If the wet/dry shop vacuum has a wet filter, replace the dry filter with the wet filter.

  3. Attach Wet Nozzle

    Wet/dry vacuums come with a variety of nozzles. One nozzle with a broad, flat head is designated a wet nozzle, though other nozzles usually will work for water, too. The wet nozzle works well for flat surfaces.

  4. Plug Into GFCI Outlet

    Because vacuuming water mixes water with electricity, it is recommended that you plug the vacuum into a GFCI outlet. Most wet/dry vacuums are double-insulated, which means that you can plug them into non-GFCI outlets if you wish.

  5. Vacuum Water

    For Water Spread Across a Floor

    Turn on the vacuum. Place the nozzle on top of the water. Hold it in place until the water under and around it is depleted. Progressively move the nozzle to a new section until all of the water is gone.

    For Large Quantities of Standing Water

    Turn on the vacuum and place the nozzle on top of the water. Wet/dry vacuums can vacuum up large quantities of standing water very quickly. One way to know if the canister is full: the motor sound changes, indicating this its speed has changed.

    Tip

    The more extensions you add to the hose, the more difficult it is to pick up water. Avoid using the extension wand, if possible.

  6. Filter Out Debris

    Open the vacuum canister. Before pouring out the water, remove any large pieces of debris.

  7. Safely Dispose of Water

    Pour the water into a proper disposal area. Water with construction debris should not be poured into garden beds.

  8. Clean and Disinfect Canister and Accessories

    Because wet/dry vacuums mix water with organisms, there is a high potential for mold and mildew growth inside the canister after use.

    Clean out the canister first with fresh water. Then pour 1 gallon of warm water with 1/4 cup of household chlorine bleach, thoroughly cleaning all areas of the canister. Run the water through the hose. Turn the canister upside-down and let it dry out. Hang the hose vertically so that it drains out. Store the vacuum and parts only after they are completely dry.

When to Call a Professional

Most shop vacuums can remove only 10 to 20 gallons of water per basin. For flooded homes, this is usually not enough to clear the property fast enough to save building materials. Instead, call a water damage restoration company.