How to Use a Shop Vac for Water

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 them 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. You may not need to insert any type of filter in your shop vac when vacuuming liquids.

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.

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 vac has two holes. One hole near the top permits replacement air to enter the container. When a hose is attached to this hole, dirt and debris can be sucked into the container. Air circulates out another hole to equalize the constant airflow in the shop vac and keep the motor cooled as it's being used.

It works much the same way with water, 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, which impedes 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.

Shop vacs are designed to be used on wet carpet to remove moisture, wet messes, and water. Use the carpet vac extractor attachment tool to remove the dirty water. This works on small patches of carpet but for larger flooded areas, you may need to take up the carpet to avoid mold growth or you might need to call in a water damage restoration professional.

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. To avoid lifting heavy tanks of water, look for a shop vac that has a built-in pump that can turn the vacuum into a water pump using a garden hose.

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.