How To Use A Shop Vac For Water Pickup

Some compressors use oil

This oil keeps the internal components from overheating, extends the life of the compressor, and enables it to create greater pressure and airflow (CFM). 

It has to be changed on a regular basis, generally once every 6 months, depending on use. 

Generally, I find myself doing odd jobs like changing the air compressor oil on slow days when I have nothing else to do. 

Today’s rainy weather has me thinking of tackling it. 

Can you use 10W30 oil in your air compressor? No, you should use a specific, single-viscosity synthetic air compressor oil.  The recommendation by air compressor manufacturers such as Campbell Hausfeld is to use a 30-weight oil. There are also detergents in motor oil that can harm the compressor.  

Using a recommended oil will protect your warranty. Using engine oil may void the warranty.

Motor oil functions differently than recommended compressor oils. There is a difference in the viscosity. Compressor oil also does not contain detergents

How To Setup a Shop Vac To Suck Up 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 a paper 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

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 dirt bag inside the collection canister as well. 

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

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 air flow. 

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

Keep in mind that these 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 canister will weigh 80 pounds when full. 

It is better to stop early and to empty it 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. 

Once you have the paper filter removed, use the squeegee type end and move it back and forth over the wet flat surfaces to remove the water. 

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 to be doings is 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 it 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.

Can You Use A Shop Vac Without A Filter?

You probably are not supposed to, and I’m sure that it shortens the lifespan somehow, but I have used mine without a filter before in both wet mode and in dry mode. (In dry mode, I’ve only done it outside, such as when cleaning out my car as it blows dust everywhere). 

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 is also handy tp leave the mesh filter on when in wet mode to keep debris from entering the motor. However, the paper filter should be always be removed. 

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. I imagine this idea comes from folks who have used the Rainbow-branded vacuum cleaners. Rainbow vacuums are designed to trap dust into swirling water. Water in a 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 13year-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. 

Dusty Vacuum used without bag or filter

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 jobsite. One employee can take a full bag of material to the dumpster while another employee throws a new bag into the shopvac and gets back to work. 

It also helps you keep your site OSHA compliant.

I also feel that shopvac bags are essential when using it as a dust collector inside your shop. It makes a massive difference in preventing the dust from flying around the shop. 

That said, I’ve mostly used shop vacs without bags. Yeah, it is messier. Occasionally I even have to get out the garden hose and deep clean the dust canister. But it mostly works out ok. 

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

What Can A Shopvac Suck Up?

Shop vacuums are so powerful. 

While they are a little more cumbersome to use, 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 coins 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 overflow mess from clogged toilets (plumbers use the heck out of theirs!)

What I really love them for is as a modified carpet extractor. I first use a spray bottle or a pump sprayer to apply a heavy layer of carpet cleaner. After the cleaner sits for 30 minutes, I use a power scrubber to agitate the carpet. Finally, I come back with the wet vac and suck the soapy water out of the carpet. After a couple of passes with the shop vaccum, I leave a few fans on the floor to make sure it dries out well.

When vacuuming large quantities of water, be on the lookout for the canister to fill and the ball mechanism to seal it off. The wet-dry vacuum motor will change pitche and it will lose all suction. 

DANGER! Do Not Use A Shop Vaccum For Flammable Liquids! Don’t vacuum flammables such as fuel, oil, dry-cleaning solvents, or alcohol. Folks don’t understand that some solvents like gasoline will melt the plastic of a shop vac. Additionally, the motor sparks in its operation and the fire is pretty much guaranteed if you try to use a shop vac on flammable fluids, 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:

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. 

Hot summer days encourage the 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 air 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 throughly — 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 valve, you will want 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 tank is full so you can carry it.

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.