A wet vac is the right tool for a spill, a soaked rug or the last film of water on a floor. Once there’s more than a few millimetres across a room, or water is still coming in, it can’t keep pace, because it has to stop and be emptied. For that you need a pump that discharges continuously, and for water on a floor, that means a puddle pump.
Collecting water versus moving it
The difference between the two isn’t power. It’s what happens to the water.
A wet vac collects. It pulls water into a tank, and when the tank is full you switch off, carry it somewhere and tip it out.
A pump moves. Water goes in, out through the hose and away, for as long as the pump runs.
Edward Barsley draws the same line in Retrofitting for Flood Resilience. He describes flood vacuums as doing a similar job to a sump and pump system, but at a much smaller volume. In practice, volume is what decides it.
How much water is actually on your floor?
It’s nearly always more than it looks. To work it out, multiply length × width × depth in metres to get cubic metres, then multiply by 1,000 to get litres.
A 4 m × 3 m kitchen with 20 mm of water across it holds 4 × 3 × 0.02 = 0.24 m³, or 240 litres. With a wet vac that has a 20-litre tank, that’s twelve rounds of filling, switching off, carrying and tipping. Each full tank weighs about 20 kg.
| Area | Depth | Water on the floor | Loads with a 20-litre tank |
|---|---|---|---|
| Hallway, 3 m × 1.2 m | 10 mm | 36 litres | 2 |
| Kitchen, 4 m × 3 m | 20 mm | 240 litres | 12 |
| Garage, 5 m × 3 m | 30 mm | 450 litres | 23 |
| Cellar, 5 m × 4 m | 50 mm | 1,000 litres | 50 |
Take the same 240 litres through a small puddle pump such as the Stream SPP2-4, which is rated at up to 70 litres per minute. At maximum flow, that’s under four minutes of pumping. Through a hose and up a step, the flow will be lower, because maximum flow is not the flow you get on site. Even so, you’re talking minutes rather than an afternoon of carrying.
Double the room or double the depth and the wet vac job doubles too. The pump just runs a little longer.
Where a wet vac is the right tool
A wet vac earns its place for small, contained jobs:
- A leaking appliance.
- A spill in a hallway.
- Water tracked in through a door.
It’s also the only option for lifting water out of rugs and carpet, which a pump can’t do at all. And it can reach into corners and along skirting where there’s no room to stand a pump.
It’s also the tool for finishing. Once a pump has taken a floor down to a thin film, a wet vac or squeegee lifts the last of it.
Before using a vac on anything more than clean water, check its manual to see whether it’s suitable for continuous wet use and for dirty water.
Where a wet vac runs out of road
There are three situations where a vacuum stops making sense.
When there’s more water than you can carry. Anything beyond a few loads becomes slow, heavy work, and the table shows how quickly those loads add up.
When water is still coming in. This is the one that catches people out. If water is seeping under a door, up through a floor or past a barrier, a vac never gets ahead. You’re emptying the tank while the floor refills behind you. A pump keeps discharging for as long as the water keeps arriving. An automatic pump does that even when nobody is there.
When the water is dirty. Floodwater can be contaminated. With a vac, every tank load is carried through the property and tipped out somewhere. With a pump, it goes out through a hose to a discharge point you’ve chosen, so give some thought to where it’s going before you start.
Whichever tool you use, the usual rules about electricity and standing water apply. Our flood pump guide covers using an electric pump safely.
Why an ordinary submersible pump isn’t the answer either
People often reach for a standard submersible pump and find it does almost nothing. Most stop drawing with 30 to 50 mm of water left behind. On a floor with 20 mm across it, that’s below where they work at all.
Puddle pumps are designed to draw from floor level:
- The SPP2-4 clears down to approximately 2 mm.
- The Stream SPK530 and Tsurumi LSC1.4S go down to around 1 mm.
That’s the difference between a floor you still have to mop and a floor that comes back to damp.
Matching the puddle pump to the job
For an occasional leak or a shallow domestic flood, the SPP2-4 is a sensible starting point. It weighs 3 kg, delivers up to 70 litres per minute with a 6 m maximum head, and clears to about 2 mm. The Small Flood Pump Kit pairs it with hose and fittings, so it’s ready to use the day the water arrives. It’s worth reading kit or pump only if you’re unsure which you need.
For bigger floors, repeat use or trade work, the SPK530 moves up to 170 litres per minute, clears to around 1 mm, and comes in 230V or 110V. The Trade & Hire Flood Pump Kit adds reinforced hose and layflat hose for longer runs.
For water that keeps coming back, an automatic pump is the step up. It’s worth knowing the trade-off. An automatic pump has to stop before it runs dry, so it leaves slightly more behind than its manual equivalent:
- The SPP2-4A starts at about 20 mm and stops at around 10 mm, where the manual SPP2-4 pumps to about 2 mm.
- For tight spots, the APP BPS100EA switches on at around 30 mm and off at around 3 mm.
The full range is in our puddle pumps collection.
The practical answer: pump first, vac to finish
For most flooded floors, the best approach uses both:
- Let a puddle pump do the heavy lifting down to a film.
- Use the wet vac for the rugs, the corners and the last few millimetres.
- Start drying.
The pump saves you the carrying. The vac saves you the mopping.
