Flooding, pits and basements: which submersible pump to drain the water?

To drain flood water, choose a submersible pump by the size of solids it passes and the flow you need. The LEO LSWM150A moves up to 26 m³/h with solids up to 30 mm. The AKS-751PWH passes 35 mm solids and starts automatically with a float switch. The LKS-300P is for clear water only (particles of 1 mm at most).

Clear, dirty or muddy water: what solids size do you need?

Maximum solids size is the largest particle that can pass through the pump without clogging it. Water that floods a yard, a basement or a garage carries sand, leaves and small debris.

• Clear water (rainwater tank, cistern): the LKS-300P, which passes 1 mm. The STK50F, a peripheral pump, is designed for lifting water from wells; its datasheet gives no particle size.
• Dirty water (flooding, yard, basement): the AKS-751PWH (35 mm), the LSWM150A (30 mm) and the LSWM100A (25 mm).
• Muddy water: even when the debris passes, sand wears the pump's parts. Stand the pump on a flat stone or a brick so it does not draw in the silt at the bottom. After use, run it for a few minutes in clean water.

The QDX1.5-32-0.75LA datasheet rates it for clean to lightly loaded water but gives no particle size. For heavily loaded water, choose the AKS-751PWH or an LSWM model.

Flow or head: which matters to drain fast?

To drain fast, look at flow first. The maximum flow on a datasheet is measured when the water is barely lifted. Maximum head is the height at which flow drops to zero. In between, flow falls as the lift rises.

In a flooded basement or yard, the pump usually only has to lift the water a few metres. High flow then matters more than high head. The head to overcome includes the vertical lift and the losses in the hose: length, bends and diameter.

A worked example: a 5 m × 4 m room with 30 cm of water holds 6 m³. At maximum flow, that takes about 14 minutes with the LSWM150A (26 m³/h), 26 minutes with the AKS-751PWH (14 m³/h) and about 2 hours 45 minutes with the LKS-300P (2.2 m³/h). Allow more time in practice: real flow falls with head and hose length.

Use a hose with the same diameter as the pump outlet: 2″ for the LSWM models, 1½″ for the AKS-751PWH, ¾″ for the LKS-300P. A narrower hose cuts the flow. Discharge the water far enough from the building that it does not run back.

The float switch: how does a sump pump start on its own?

The float switch starts the pump when the water level rises and stops it when the level falls. The pump then works unattended, even at night during a storm. It also prevents dry running, which most submersible pumps do not tolerate: follow the manual.

Three of our models have a float switch: the AKS-751PWH, the LKS-300P and the QDX1.5-32-0.75LA. The LSWM100A, LSWM150A and STK50F datasheets do not mention one. Keep an eye on these pumps and switch them off once the water is gone.

A sump pump lifts water out of a pit that sits lower than the drain. If the pit must empty itself, pick a model with a float switch. Leave enough room around the pump: the float must rise and fall without touching the wall or the cable.

The 6 LEO submersible pumps in one table

The values below come from the LEO datasheets. “Not stated” means the datasheet does not give the value.

• Flooded basement, yard or garage: the LSWM150A for the highest flow, the AKS-751PWH for automatic operation and the largest debris.
• Wastewater, inspection chamber or sump pit: the LSWM100A and LSWM150A, built for sewage. Their datasheets do not mention a float switch, so keep an eye on them while they run and switch them off by hand.
• Rainwater tank: the LKS-300P.
• Water that must rise high or travel far (upper floor, distant drain): the QDX1.5-32-0.75LA, with a float switch. Its flow is lower.

These pumps are not designed for deep boreholes. The full range is on the Submersible Pumps page and on the LEO brand page. For a home water supply (pressure, well, tank), see our guide Which water pump for a house.

No electricity: a petrol pump or a generator?

When the power is off, you have two options: a petrol water pump, or an electric pump running on a generator.

A petrol water pump stays out of the water, at the edge of the flooded area, and draws the water through a suction hose. The Bison BS30 and BS40 datasheets give a maximum suction height of 7 m; in practice, set the pump as close to the water level as you can. The Bison BS30 moves up to 50 m³/h and the BS40 up to 60 m³/h. Their datasheets do not state the solids size they accept.

Never run a petrol pump in a basement, a pit, a garage or any enclosed room, or near a doorway or window: its exhaust contains carbon monoxide, a deadly gas. Our guide to 2-, 3- or 4-inch petrol pumps compares the BS20, BS30 and BS40.

On a generator, size for the power in kW and for the motor's starting surge. Our kVA or kW guide and our Generator Finder help you size it. Set the generator up outdoors, in a dry spot away from the water: see our guide to installing a generator safely. We also offer generator rental.

Electrical safety: what does IPX8 mean?

An IPX8 rating means the device withstands prolonged immersion. The AKS-751PWH and LKS-300P datasheets state it; the other datasheets do not give a rating. The pump body is made for water, but the plug, the extension lead and the distribution box are not.

• Keep the plug, extension connections and distribution box above the water line and out of the rain. Our guide to IP ratings for junction boxes and enclosures explains which rating to choose.
• Protect the circuit with a 30 mA residual current device (RCD), fitted by an electrician.
• Unplug the pump before you touch it or step into the water.
• Lower and lift the pump by its handle or a rope, never by the power cable.
• Do not exceed the maximum immersion depth: 7 m for the AKS-751PWH and LKS-300P, 10 m for the STK50F.

Delivery, installation and quotes

We deliver in Kinshasa and to the other provinces of the DRC. We provide installation, maintenance, after-sales service and spare parts: see our services. Our showroom is at No. 26, Avenue des Huileries, Gombe, opposite the INRB.

Ask for a quote on WhatsApp at +243 903 005 060 with the type of water, the volume to drain, the height to lift and the hose length. Price on request.

Frequently asked questions

Which pump should I use to drain a flooded basement?

A dirty-water pump. The LEO LSWM150A moves up to 26 m³/h with solids up to 30 mm. The AKS-751PWH passes solids up to 35 mm, and its float switch starts and stops it automatically.

Can I use a clear-water pump in muddy water?

No. The LKS-300P only passes particles up to 1 mm: sand and debris will block it or wear it quickly. Keep it for a rainwater tank and use a dirty-water pump for flooding.

Will a submersible pump run on a generator?

Yes, if the generator supplies the right voltage and enough power at start-up. The datasheets give 180–220 V / 50 Hz for the LSWM models and 220–240 V for the STK50F. Check that the generator's output voltage (220 V or 230 V depending on the model) falls within that range: a 230 V generator is above the LSWM range. Set the generator up outdoors in a dry spot, never in the flooded room.

Sources: LEO datasheets (AKS-751PWH, LKS-300P, LSWM100A, LSWM150A, QDX1.5-32-0.75LA, STK50F) and Bison datasheets (BS30, BS40); general electrical safety practice.