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Can a wet vac effectively be used as a pump to move water?

I figure if a basement floods, that this can serve as double duty.

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City employee, talked the boss into buying us a shop vac about 5 years ago ,so i saw the one with a built in "water pump",at Lowes and gave it try. Why not? Not my money if it turns out to be junk, lol. I used it to clean out one of our sump pump pits at the bottom of one of our dry wells at a sewer pump station . everything is around 40 feet straight down in the ground. We all had serious doubts about this"pump" but if it worked it would have saved several hours of work, not having to send the tank up on the hoist after filling it up to be emptied. Hooked a water hose to the pump discharge, put on the pump extension /filter in the tank,ran the water hose straight up 40 feet and about another 10 feet to the toilet. Can you believe it WORKED? ! And worked perfectly. Only once or twice i had to stop so the pump could catch up from what i was sucking up, but 2.5 inch suction hose VS. 5/8 inch discharge, plus the height, man you can not ask for better. It was a full stream and lots of pressure on the discharge side,probably could have pumped 80 feet straight up. 5 out of 5 stars. Buy it. I protect that shop vac like its my own,dont want any monkeys screwing it up.

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A pump can operate continuously to move water between two locations. The wet vac will suck water into the cannister, but you'll need to continuously stop, and dump that water, before it reaches the top of the vacuum. If you're looking at a flooding risk, I'd want the pump.

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  • Thanks, I'm curious about the evacuation of water. What if you just place the body outside of the canister which it usually calls home? I wouldn't expect this to be a continuous proposition, but only in case of emergency.
    – mbrownnyc
    Aug 29, 2011 at 13:05
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    @mbrownnyc, Water isn't sucked through the vacuum motor, it's sucked into the canister body via an air vacuum created by the motor on top. The hose is attached to the canister, not the vacuum. I also don't think you'll see a lot of suction power from smaller shop vacs, enough to pull up a spill, but not enough to suck a bucket of water up 5 feet vertically.
    – BMitch ♦
    Aug 29, 2011 at 13:18
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    In my experience, most shop vacs -- even the most expensive "contractor-grade" ones -- will not be able to maintain the pipe full of water: you have to suck a mix of air+water or else it will just stall. A trash pump will work the best with large amounts of water (can be rented at any rental place), and a regular sump pump will be the cheapest and most effective option.
    – gregmac
    Aug 29, 2011 at 22:57
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Some Shop Vacs have a "water pump" feature. You can attach a garden hose to a side port on the vac, and rather than just dumping the water in the canister, it will actually pump the water to another location.

http://www.shopvac.com/wet-dry-vacs/default.aspx?feature=12&featureName=Water+Pump

If you do not have such a vac, you can suck water until the canister fills up. Then you have to dump the water somewhere. (Note: A shop vac full of water is really heavy.)

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  • This is very interesting! Thanks! I assume that gregmac's comments on the above answer are "modifiers" of this.
    – mbrownnyc
    Aug 30, 2011 at 13:09
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    I haven't ever used a shopvac that actually had this "water pump" feature, so I can't comment.
    – gregmac
    Aug 30, 2011 at 22:35
  • Great feature. Though if I'm ever vacuuming up so much water to need this, I think I'd want a sump pump.
    – BMitch ♦
    Aug 31, 2011 at 11:38
  • Shop Vac water pump feature is advertised for draining a hot tub. I haven't used it for anything that big, just a few gallons.
    – myron-semack
    Aug 31, 2011 at 12:43
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Drill a hole near the bottom of the vac canister and plug it; when the canister is half full remove the plug and water will drain out of the canister but still keep a vacuum as long as water doesn't empty. Size the hole properly: not so small that the canister fills, or so large that it empties too quickly.

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    How do you determine the size of the hole, or would you just use trial and error?
    – Tester101
    Dec 31, 2012 at 18:23
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Just use the hose from the shop vac. Drained my 560 gal spa in less than 15 min. Submerge hose in water to prime and pull out end with extensions to drain. works like a charm.

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    Were you actually using the shop vac, because it sounds like you were just siphoning out the water.
    – Niall C. ♦
    Feb 14, 2013 at 17:12
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    ...and if you're trying to siphon a basement, it won't work because you'll have negative hydraulic head.
    – alx9r
    Feb 15, 2013 at 2:05
  • As noted elsewhere, some shop vacs apparently can pump to some degree.
    – keshlam
    Oct 26, 2015 at 12:40
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I'm draining my pool cover right now with the shop vac. Run it until the water hits the top. When you pull the lid motor you've already created the suction you need. It is slow but steady. No need to drill a hole in the side. It just pours out the top.

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I use mine twice a year to dredge the bottom of a 15,000 gallon pool that is now a pond. Detritus sucks up easily, I just stop before it fills and drain it into the grass... then repeat. Takes an afternoon but the fish and grass are both happy.

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I fit a 5-gallon bucket with check valve in the bottom, and water intake near top, and vacuum connection in another hole in top. I apply vacuum to fill bucket, and the check valve stops air from coming in, then stop vacuum to let drain out bottom through check valve. Put on timer on/off for continuous pumping.

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