Guide · 7 min
How do you pump water out of a flooded area with a dewatering pump?
Also called: dewatering pump, water pump
By the SIMAQ technical team · Grupo ConstruMarket ·
Short answer
Set the pump on firm ground, as close to and as low as possible relative to the water; fill the casing (prime it), fit the strainer on the suction and send the discharge well away from the area. With the SQWP30 PRO (3″, 30 m³/h) or the SQWP40 PRO (4″, 40 m³/h), time is easy to work out: water volume ÷ flow = pumping hours, bearing in mind real flow drops with height and hose length.
Work it out with your numbers3″ and 4″ pumps
max suction height
total head
3″ or 4″ pump?
The difference is flow and how high it can push the water. The 4″ moves a third more water per hour and pushes higher; the 3″ is lighter and enough for basements, trenches and medium volumes.
| Spec | SQWP30 PRO (3″) | SQWP40 PRO (4″) |
|---|---|---|
| Suction & discharge ports | 3″ | 4″ |
| Discharge capacity | 30 m³/h | 40 m³/h |
| Total head | 13 m | 16 m |
| Max suction height | 8 m | 8 m |
| Engine | Loncin G200F, 6.5 HP | Loncin G270F, 9 HP |
| Use it for… | Basements, trenches, ponds, medium volumes | Large flooded areas and higher or farther discharge |
How long it takes: the dewatering maths
Work out the water volume: length × width × depth, in meters. Divide it by the pump's flow and you have the hours. Example: an 8 × 6 m basement with 0.5 m of water holds 24 m³. With the 4″: 24 ÷ 40 = 0.6 h, about 36 minutes. With the 3″: 24 ÷ 30 = 0.8 h, about 48 minutes.
Treat that result as the minimum. The flow on the spec sheet is the pump's maximum; on site it drops the higher you have to lift the water and the longer the hose. And if water keeps coming in (rain, seepage), add it. In practice, plan for more time than the maths gives.
Step by step
- Set the pump on firm, level ground, as close to and as low as possible relative to the water.
- Connect the suction hose with the strainer at the end and check the coupling doesn't let air in.
- Fill the casing with water (prime it) before starting: never start it dry.
- Start, throttle up and wait for water to come out of the discharge.
- Route the discharge far from the area so the water doesn't come back.
- Keep an eye on the strainer and fuel level while it runs.
Short suction, distant discharge
Both pumps have an 8 m maximum suction height, but that's the limit, not the target. The shorter and lower the suction, the better the pump primes and the more water it moves. Total head (13 m or 16 m) is everything the pump can push, adding suction, discharge and hose losses: as you approach that number, flow drops sharply.
The suction hose must be reinforced so it doesn't collapse under vacuum. A soft hose closes up and the pump runs without water.
If this happens, do this
| If… | Do this |
|---|---|
| It won't draw or prime | Refill the casing and check no air is getting in through the coupling or hose |
| It moves little water | Clean the strainer and move the pump closer or lower |
| The suction hose collapses | Swap it for a reinforced hose |
| Water flows back into the area | Extend the discharge and take it farther or lower |
| The water carries fuel or chemicals | Don't pump it with this pump; tell the site manager |
Safety with flood water
Before going into a flooded basement or building, cut the power. Don't run the gas pump in an enclosed space: carbon monoxide builds up. And flood water carries mud, trash and stones: the strainer isn't optional. Your advisor confirms the solids size each pump can handle.
Do it with your numbers
Which pump is enough for you?
≈ 300 liters per minute.
Suction + discharge + ~10% extra for hose friction.
Water pump SQWP30 PRO
3″ · LONCIN G200F · total head 13 m
16 m³/h
estimated at 6 m of head
View detailsWater pump SQWP40 PRO
4″ · LONCIN G270F · total head 16 m
25 m³/h
estimated at 6 m of head
View detailsNameplate flow is measured at 0 m of head — at your jobsite's real head it's always lower. Keep at least 15% reserve, keep suction short and airtight, and always run the strainer with solids.
Practice it
Simulator: pump out the trench
Pick pump and hose and start it: the water drops, the curve moves and you see how long it takes.
Common mistakes
- Starting the pump dry, without priming the casing.
- Pumping without a strainer: stones and rags clog or damage the impeller.
- Placing the pump far from and high above the water, with a long suction line.
- Using a soft hose on the suction: it collapses.
- Discharging water where it runs back into the excavation.
- Going into a flooded basement with the power on.
Takeaway
Pump close and low, casing primed, strainer on the suction and discharge far away. Pick the 3″ (30 m³/h) or the 4″ (40 m³/h) by volume and height, and estimate time as volume ÷ flow at minimum. Request a quote here and an advisor will contact you during business hours.
Keep going
Take it to the job site
Print the checklist to go over it on site, or send the guide to your crew.
Frequently asked
Which pump do I need, 3 or 4 inch?
For basements, trenches and medium volumes, the 3″ (30 m³/h). For large flooded areas or if you need to lift water higher, the 4″ (40 m³/h, 16 m total head).
How long does a pump take to remove the water?
Volume ÷ flow. 24 m³ with the 4″ is about 36 minutes at minimum; with height and a long hose, it takes longer.
Why won't my pump draw water?
It's almost always lack of priming or air getting in at the coupling. Fill the casing, tighten the coupling and check the suction hose isn't collapsed.
How high can the pump draw water from?
Up to 8 m on both SIMAQ pumps, but the lower the suction, the more water it moves.
Does it handle muddy water?
Yes, it works for jobsite and flood water, always with the strainer on the suction. Your advisor confirms what solids size each model takes.
SIMAQ · Job site checklist
How do you pump water out of a flooded area with a dewatering pump?
Set the pump on firm ground, as close to and as low as possible relative to the water; fill the casing (prime it), fit the strainer on the suction and send the discharge well away from the area. With the SQWP30 PRO (3″, 30 m³/h) or the SQWP40 PRO (4″, 40 m³/h), time is easy to work out: water volume ÷ flow = pumping hours, bearing in mind real flow drops with height and hose length.
Step by step
- Set the pump on firm, level ground, as close to and as low as possible relative to the water.
- Connect the suction hose with the strainer at the end and check the coupling doesn't let air in.
- Fill the casing with water (prime it) before starting: never start it dry.
- Start, throttle up and wait for water to come out of the discharge.
- Route the discharge far from the area so the water doesn't come back.
- Keep an eye on the strainer and fuel level while it runs.
Avoid
- Starting the pump dry, without priming the casing.
- Pumping without a strainer: stones and rags clog or damage the impeller.
- Placing the pump far from and high above the water, with a long suction line.
- Using a soft hose on the suction: it collapses.
- Discharging water where it runs back into the excavation.
- Going into a flooded basement with the power on.
Job site:
Date:
Supervisor:
Scan it for the full guide, with video and FAQ
https://simaq.pro/en/recursos/achicar-zona-inundada-con-motobomba
