How To Use A Shop Vac For Water Pickup

The first shop vac I owned was a small one I bought from Harbor Freight.

It was amazing. The first time that water came in under our garage, I could suck it up and send it back outside.

And then the basement flooded. While that required a bigger shop vac and some fans (which I borrowed from a friend), I became a huge fan of the shop vac’s versatility.

How To Setup a Wet-Dry Vac To Vacuum Water 

The first thing you need to do is to switch it from dry vac mode. Begin by removing the paper cartridge filter and any paper interior parts (such as the dry dust bag). 

  1. Unclip the blower unit motor from the collection tank, lift it up and look at the filter situation. 
  2. Remove the Paper Filter
  3. Re-attach the motor housing 
  4. Plug it into a GFCI outlet
  5. Keep the vacuum upright
  6. Clean the collection tank with warm water and soap when finished

Mine has a foam filter (it looks like black mesh) that stays in place for both wet and dry mode. You’ll notice that it looks like a foam sleeve over the filter cage.

Some of the shop vacuums may have a dirtbag inside the collection canister as well. 

Once you have removed the paper filter as well as the dust bag and emptied the canister of dirt leftover from the last use, your shop vac is ready to use in wet mode. 

Once you have the vacuum cleaner put into wet mode, use the squeegee type end and move it back and forth over the wet flat surfaces to remove the water. 

There is a ball float inside your wet/dry vac. As the water level in the vacuum increases, this raises the float up until it seals the vacuum. You’ll hear the distinct whine as the motor increases when the float seals the airflow. 

This ball float helps to keep water out of the motor. It also helps to protect the motor from water should the vacuum tip over. 

A wet-dry vac can get extremely heavy depending on the amount of water it holes. Water weighs about 8 pounds per gallon. A large shop vac with a 10-gallon collection tank will weigh 80 pounds when full. 

It is better to stop early and empty the wet dry vac more frequently so that you can still manage the canister and get it outside. 

Alternatively, you can use a basic water pump to remove the water from the canister. (Any hardware store will have water pumps you can buy cheaply)

When finished, wash the collection tank with soap and warm water to prevent mildew and stink.

Here is a handy video that demonstrates all of these steps:

Electrocution Risks With A Shop Vac

Any time water and electricity are near each other, you want to be careful. 

The last thing you want is to be standing in your flooded basement while the power cord is submerged behind you in the water!

Water and electricity are a deadly combination! 

Here are some best safety practices:

  • Plug vacuum cleaner into a GCFI outlet
  • Have a second person to help you move equipment and spot for electrical hazards
  • Make sure your cords and equipment are in good shape and not frayed
  • Keep cords from being submerged
  • Keep the Vacuum from being Submerged
  • Keep the Vacuum from tipping upside down into the water.
  • Have one person “babysitting” the vaccum and cords.

Turn off, Drain, Clean and DRY Your Shop Vac

You absolutely must unplug, empty, and dry your wet vac after use. The water mildews extremely quickly. It is normally mixed with dust and dirt and I find that it can get smelly, even after only 6 hours of sitting. 

A wet filter attracts mildew, so remove it from the unit and hang it dry.

Hot summer days encourage bacterial growth even more quickly. 

Even if the job isn’t done, take a minute to drain the tank and leave the motor off of the tank so it can completely dry.

When you are done, you will want to get a towel and dry out the tank completely. You might even consider using some dish soap and warm water to clean it thoroughly — especially if you have been using it for dog poop or urine.

How To Drain Your Shop Vac

To drain your shop vac, you will either be able to take advantage of the small valve at the base of the canister. If you aren’t lucky enough to have a drain plug, you will have to remove the top and tip it over. 

Or, you can use a small water pump to pull the water out of it. 

Shop Vacs can be very heavy to carry since water weighs 8 pounds per gallon. You may wish to stop before the collection tank is full so you can carry it.

Not all shop vacs are the same, so consult your owner’s guide if my instructions aren’t matching your vacuum.

Can You Use A Shop Vac Without A Filter?

Filters are cheap. Vacuums are expensive. Unless you want to run the risk of damaging your shop vacuum, always use a filter.  Using it without a filter can cause it to clog. 

I like to keep some extra filters on hand. 

Should you remove the filter when using it in wet mode? The black mesh filter can be used in dry mode but should also be used in wet mode to keep debris from entering the motor.

The key thing with a filter is that it keeps dust from being blown back out. Without a filter, your vacuum just picking up the dust and blowing it back out around the room in fine particles. 

Does the Water Replace The Role Of A Filter? – I’ve seen people try to add water to the bottom of their wet-dry vacuum to make it trap dust like a filter when working in dry mode. I imagine this idea comes from folks who have used the Rainbow vacuum cleaners. Water in a wet-dry shop vac may help trap some dust, but the water is being “frothed” instead of swirled, and it creates a mess of bubbles that can slip past the float and seize the motor. (My 13-year-old self figured this out the hard way, once). In dry vacuum Mode, always use the paper filter. 

Can You Use A Shop Vacuum Without A Bag?

One of the cool features of a high-end shop vac is that they have an additional filter bag that can go down inside of the canister. 

This bag helps to trap debris and further reduces the dust that flies around when in dry vac mode. 

These bags are handy for high-speed cleanup of the job site. One employee can take a full bag of material to the dumpster while another employee throws a new bag into the shop vac and gets back to work. .

I also feel that vacuum bags are essential when using them as a dust collector inside your shop. The bags make a massive difference in preventing the dust from flying around the shop. 

Whatever you do, you must remove the bag before vacuuming wet material. 

Dusty Vacuum used without bag or filter

What Can A Shop Vacuum Cleaner Suck Up?

I’ve known folks who use them as their primary household vacuum cleaner. 

You can suck up anything. I’ve used them to clean up job sites and watched them suck up screws, nails, coins, and small bits of wire. I’ve cleaned out cars with them and sucked up lollipops and aged chicken nuggets. 

Where they really shine is in the nasty side of life. You can vacuum pet hair, urine, and even dog poop. They work great for liquid spills and for cleaning a flooded basement from a broken pipe, heavy rain, or the overflowing mess from clogged toilets (plumbers use the heck out of theirs!)

DANGER! Do Not Use A Shop Vaccum For Flammable Liquids! Don’t vacuum flammables such as fuel, oil, dry-cleaning solvents, or alcohol. Solvents like gasoline will melt the plastic of a shop vac. It is likely to explode as the gasses build up inside the canister and then ignite.  Thankfully, Youtube doesn’t disappoint and we have excellent footage of a shop vac blowing up under misuse in this video:

Should You Use A Shop Vac To Empty Your Koi Pond?

Water pumps are a better option for emptying koi ponds

Most of us have used a shop vac to drain a basement before. It makes sense that it might work to suck the water out of your pond at the end of the season. 

What I’ve found is that you are constantly stopping to drain the vac. It’s an endless, slow, process, and I imagine that it is hard on the motor. 

What I would recommend is that you purchase a cheap pump. Small submersible pumps only cost around $30 to $60 and they last for years. 

These pumps also work great when draining a flooded basement.

About Zachary Drumm

Hey! My name is Zachary Drumm! This site allows me to try these tools out, piddle around in the garage, and create fresh content for you. When it comes to tools, home improvement, and being a “shade tree mechanic,” you’ve come to the right spot.