Colglo Blog

A guide to using small sump pumps for domestic flood defence

Posted by Collister & Glover on Jan 9, 2020 12:57:52 PM
Collister & Glover

What is a Sump Pump?


Having so far had one of the wettest winter periods in years and more rain expected across large areas of the UK, the saturated ground means that if you are under threat from ground water it's time to take precautions and prevent flooding. A simple sump pump can help stop flood water from entering a building. This quick guide shows how they can be used successfully. 

A submersible sump pump should never be allowed to run dry which generally means there is some installation work required to create a chamber or housing. A submersible pump then rests in the water within the chamber. Nearly all pumps have a waterproof housing, with the pump itself at the bottom of the chamber, and the outlet pipe near the top. A flat screen or grate covers the bottom of the pump to keep out debris. When the pump turns on, water is sucked up through the grate and routed into the pipes and out of your home. The illustration below shows a chamber made with bricks but it can be equally effective when using a plastic bin in a hole. For all installations, there are a few basic rules.


Sump pumps come in a wide range of flow rates and many can be installed both internally or externally, they are suitable for pumping muddy water that may contain small particles and small debris.

Dealing with flooding

Flooding in the UK usually occurs when the ground is low lying or near to a watercourse, a stream or pond.  To prevent building basements flooding or prevent groundwater pooling on ground, which can add to the problem, it is best to install the pumps permanently. If possible, match the pump size to the amount of expected flood water. For efficiency, also match the pump model outflow to the outlet pipe diameter.


Sump pumps are suitable for drainage of flooded basements, cellars and garages, emptying tanks or cisterns or to prevent flooding when installed in rainwater collector wells. As a portable pump they are deployed in emergency situations to drain water from flooded premises.

DAB Nova Pumps

The Nova range by DAB are suitable for submersible pump stations, they are specifically manufactured to deal with excess rainwater and drainage in residential buildings. The pumps can be operated manually or automatically. They are also used as portable pumps for emergency use.

Nova 180, Nova 600 are suitable for fixed or portable installations, they are available in both an automatic version with an integrated float switch or a manual version.


DAB Nova pumps have been redesigned recently making them ergonomic to use, more reliable and corrosion resistant.

The pump body, impeller and the suction grille are made from a techno-polymer and the motor shaft is manufactured from stainless steel. Thermal protection is incorporated into all of the single-phase pump versions. The dry run usage limit is approximately one minute.  For external use, a 10-meter power cable is mandatory to comply with European standard EN 60335-2-41.

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Installing Sump Pumps for flood defence

Note: Sump pumps cannot be used in swimming pools, ponds or tanks in which people are present, or for pumping hydrocarbons petrol, diesel fuel, fuel oils, etc.

In fixed pumping stations, install a sump pump switch. Sump pump switches are typically installed to ensure that the water from a drainage system will not overflow. Running a non-submersible pump dry will quickly damage it. The implementation of a correctly matched switch will help protect the pump by shutting it off if the supply of water was restricted or fails. For efficiency ensure that any housing pit is built to match the pumps dimensions, then bear in mind the quantity of water arriving and the flow rate of the pump.

Pumps with a float switch are started up automatically when the water level rises. Single-phase motors have built in thermal overload protection and are connected directly to the mains.

The pump must be installed in a vertical position and sufficiently immersed in water.


For long periods of inactivity in winter, at a temperature below 0°C, make sure that there is no water residue at the base of the pump, frozen water will prevent the pump impeller turning.


Sump pumps are usually provided with a carrying handle attaching a rope to the carry handle allows it to be lowered into deep holes. Always use the handle when moving the pump. Lifting the pump by the float switch or pipe outlet will cause damage. 


Sump Pump Pipe Positioning and Bases

It is important when installation is in a pit or a sump that the weight of the pipes is supported separately.

Pipe Supports

If your pump is installed without a base. Provide enough space beneath the support, especially if it is to be installed in a pit where the bottom can become particularly dirty. Try to leave a space at the pump bottom that will allow water to flow.

Maintenance of the Sump Pump

If the pump has been used with water that has left a thick deposit, rinse it down after use, ideally with a powerful jet of water from a hose.


If you are going to use a pump in a sump or a pit permanently, design the pit to match the size and specification of the pump. Provide a housing pit with dimensions slightly bigger than the pump dimensions. The diagram below shows a pit that has been built considering the quantity of water arriving, the flow rate of the pump and the external dimensions of the pump. If the pump uses a float arm, remember the horizontal dimension should be wide enough to allow the arm to be horizontal.

The discharge pipe, on the right of the diagram, allows water from the sump pump to be properly drained away from the building.  You should keep an eye on the discharge pipe and make sure it’s in good condition. Make sure the pipes are directing water away from your property at a safe distance and that they are tightly and correctly connected.


Problem solving sump pump problems.

1. Pump has no water delivery

The intake grid, or the delivery pipes could be blocked or the impeller is worn or jammed.

If the pump does not stop at a low water level look at the float switch and ensure that it can move freely.

2. Float switch problems


A sump pump float switch controls the sump pump motor, telling it when to start and stop pumping by detecting the water level in the pump station. The float switch needs enough space to freely float and sink to work correctly. If there’s an obstruction in or around the float switch, then the sump pump cannot work correctly. If left for a long time, this can burn up the pump’s motor and ruin the pump.

3. No water from the Discharge Pipe

Make sure the pipes are directing water away from your property at a safe distance and that they are tightly and correctly connected. If you notice any damage to the pipes or find that they are clogged, get help or clean them right away. These problems can prevent efficient drainage.

4. Debris in the Pump

If any sort of debris gets sucked up into the pump, it can cause a problem with the sump pump system. Take the necessary measures to prevent debris from getting into your sump pump. It shouldn’t sit on small pieces of gravel or loose silt, which can be sucked up into the pump. If you want your sump pump to sit on gravel, use larger-sized gravel or rocks that cannot enter the pump. Otherwise, try placing your sump pump on a flat, stable brick surface.


5. General maintenance

Test your sump pump twice every year, once just before spring and once before Autumn. The testing ensures the pump is working efficiently before being tested by a full downpour. If the pump fails you will have time to address any problems.

Simply pour some water into the sump pit until the float switch is activated. the pump should start to transfer water and the water level in the pit should drop slowly. Once the float switch reaches its minimum trigger point the pump should turn off.

Most sump pumps are wired directly into the buildings electrical system, ideally a sump pump should also have a back-up battery or a reserve power system such as a generator.

A lack of power can be problematic during strong storms that are powerful enough to cause a full power outage and generally this is when you need the sump pump most.


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Topics: Colglo, pumps, DAB, Flooding, Flood Defence