Flood pumps can play an important role in flood protection, flood response and recovery. Traditionally, flood defences focused heavily on barriers, walls and gates, but stopping water at a boundary is only part of the problem.
Rain may still fall inside the protected area. Water can seep beneath or around defences. Groundwater can rise. Drainage can become overwhelmed. In all of these situations, water may collect on the supposedly "dry" side of a flood defence.
A flood pump gives that water somewhere to go.
For a property protected by flood barriers or walls, a pump can remove seepage and rainfall before it reaches a damaging depth. As part of a Property Flood Resilience (PFR) scheme, a pump can help manage water that does get inside. Pumps are also widely used to clear cellars, basements, garages, yards, plant rooms, construction sites and other low points where water collects.
There is no single type of "flood pump". The right pump depends on the water, the rate it is arriving, how low you need to remove it, how far it has to travel and whether somebody will be there to operate the pump.
This guide explains the different options, how to size a flood pump properly and which pumps from our range suit different applications. If you already understand the basics and want a quick recommendation, you can also use our Pump Finder.
What is a flood pump?
A flood pump is a water pump selected for removing or controlling floodwater. It is an application rather than one specific type of pump.
Depending on the situation, a flood pump might be:
- a low-level puddle pump;
- an automatic submersible drainage pump;
- a dirty-water pump;
- a high-flow dewatering pump;
- an engine-driven pump where mains electricity is unavailable; or
- a permanently installed sump or packaged pump station.
For many domestic and commercial flooding situations, particularly shallow water across a floor, a puddle pump is the most useful starting point. Unlike a conventional submersible pump, a puddle pump is designed to continue operating at very shallow water levels.
That matters during flooding. Removing 100mm of water is one thing. Removing the final few millimetres from a cellar, garage or finished floor is another.
Which type of flood pump do I need?
| Situation | Usually start with |
|---|---|
| Shallow floodwater across a floor | Puddle pump |
| Cellar or basement that may flood while unattended | Automatic puddle pump |
| Recurring flooding requiring a permanent installation | Packaged sump or pump station |
| Muddy or silty water containing grit or small solids | Dirty-water pump |
| Large volumes of water that need moving quickly | High-flow pump |
| Flood response where no suitable electrical supply is available | Engine-driven pump or appropriately designed backup arrangement |
| Water collecting behind a flood barrier or flood wall | Puddle or automatic flood pump, depending on whether somebody will be present |
The three main categories of flood pump
Most flood pumps fall into one of three categories. After surveying hundreds of flooded properties across the UK, we see the same mistake over and over: people buy the wrong pump for the job, so it is worth understanding the difference before comparing models.
1. Puddle pumps
Best for: pumping shallow water. Think: seepage, rainwater on floors, flood water leaking in.
Puddle pumps can clear water down to very low levels, much lower than a standard sump pump, which makes them ideal for:
- Water sitting on flat floors
- Small leaks
- Seepage through the ground or the walls
- Cleaning up after a flood
They are lightweight, portable, and need no chamber or pre-installation work. You simply drop one into the water and away it goes.
Good to know: puddle pumps run with very little water around them, but they do not always have the highest flow rates. They are perfect for mopping up, not for moving huge volumes fast. Browse our puddle pumps, or read what is a puddle pump for more.
2. Submersible (sump) pumps
Best for: groundwater, basements, long-term protection and installations. Think: part of your permanent flood resilience setup.
A sump pump sits inside a chamber, and automatic versions work using a float switch. When water levels rise, the pump kicks in and moves the water away before it reaches floor level. Sump pumps are great for:
- Groundwater entering basements
- Seepage rising through cracks and joints
- Keeping cellars dry
- Managing rainfall that collects behind flood barriers
- Passive flood defences, installed in chambers with automatic float switches
They typically have higher flow rates than puddle pumps and are extremely reliable when installed properly. For most homes with flood or groundwater issues, a packaged pump station is the gold standard.
Important: a sump pump must be submerged to stay cool. It cannot run dry, so it needs a proper chamber. See our submersible pumps.
3. Engine-driven pumps
Best for: large volumes of water, outdoor use, and areas with no power. Think: emergency backup during storms or power cuts, or rural areas off the mains.
Engine pumps move a lot of water very quickly. Because they run on petrol or diesel, they are ideal when:
- Power may fail, which often happens in storms
- You need to drain a garden, yard or large area fast
- You are working in a remote or rural location
If your property relies heavily on electric pumps, it is wise to keep an engine pump as a backup. If the power goes out, your whole flood system is useless without one.
Important: engine pumps cannot be used indoors, due to fumes and fire risk, and they are noisier than the other two types. They also usually require priming and more oversight. See our engine-driven pumps.
Most homes benefit from a combination
Most homes benefit from a combination:
- Sump pump: installed protection for groundwater and seepage.
- Puddle pump: quick response for surface water and post-flood clean-up.
- Engine pump: backup when the power fails, or when you need high flow fast.
If you only choose one, make sure it suits the type of flooding you actually experience, not the one that looks cheapest or most powerful on paper. For specific models at each budget, see the manual and automatic pump sections below, or use the Pump Finder.
How to choose a flood pump
The best flood pump is not simply the pump with the highest advertised flow rate. It needs to suit the water you are pumping, how quickly that water is arriving and the route through which it has to be discharged.
There are six main things to consider.
1. What is in the water?
Start with the water itself.
Clean rainwater and lightly silty floodwater can be handled by many puddle and drainage pumps. If the water contains more grit, sand, leaves, sediment or soft solids, you need to pay attention to the pump's free passage, which is the size of suspended solids it is designed to pass.
A pump with a very high flow rate is little use if its inlet repeatedly becomes blocked.
For muddy, sandy or more contaminated non-foul water, look at our dirty-water pumps. Sewage or foul water requires a pump specifically designed for that duty rather than an ordinary flood or puddle pump.
2. How low do you need the water to go?
This is particularly important when flooding is inside a building.
Many standard submersible pumps require a reasonable depth of water around them and stop pumping while water is still covering the floor. A low-level puddle pump is designed to continue operating much closer to floor level.
Some manual puddle pumps in this guide can reduce standing water to around 1 to 2mm under suitable conditions.
That can be the difference between removing most of a flood and actually leaving a floor ready for the remaining moisture to be cleaned or dried.
3. How much water do you need to move?
Pump flow is normally expressed in litres per minute or litres per hour.
A small domestic flood or slow groundwater seepage may not need an enormous pump. A rapidly filling basement, large commercial area or major flood response may require considerably more capacity.
The important question is not simply "what is the biggest pump?" It is whether the pump can remove water at least as quickly as it is entering the area you are trying to protect.
Where very large volumes have to be moved, see our high-flow water pumps.
4. How high and how far are you pumping?
This is where pump selection becomes more technical.
A pump has to work against resistance, referred to as head. Vertical lift is particularly important, but the hose itself also creates resistance. Long hose runs, small-diameter hose, bends, valves and fittings all reduce the amount of water that reaches the discharge point.
This means a pump advertised as having a maximum flow of 170 litres per minute will not necessarily deliver 170 litres per minute at the end of your hose.
The higher and further you pump, the lower the flow will normally become.
If you know roughly how high the water needs to be lifted and the length and size of your hose, use our Water Pump Performance Calculator. We also have a guide explaining how to read a pump curve.
5. Manual or automatic?
A manual pump operates for as long as it is switched on. This makes manual pumps particularly useful for flood response, clean-up and situations where somebody will be present to monitor the pump.
An automatic pump detects rising water and starts without somebody having to switch it on. It then stops again when the water level falls.
Automatic operation makes particular sense for a cellar, basement, garage, plant room, lift pit or other area where water may arrive overnight or while the building is unoccupied.
For more detail, see our guide to pumping water away automatically at floor level.
If you are weighing up the two approaches, our guide to manual versus automatic flood pumps compares them in more detail.
6. Where will the water go?
Think about the discharge point before buying the pump.
There is little benefit in moving water quickly if it cannot safely get away, flows back towards the building or contributes to flooding somewhere else.
You should also not assume that the nearest drain, sewer, ditch or watercourse can automatically be used. Depending on where and how you are discharging floodwater, permission may be required from the relevant authority or asset owner.
During a flood, remember that the drainage system itself may already be overwhelmed. Pumping into a drain that is surcharging can be ineffective and may simply contribute to water returning towards the property.
Understanding maximum flow and maximum head
Pump specifications commonly show a maximum flow and a maximum head. These are useful figures, but they are not achieved at the same time.
Maximum flow is achieved where the pump is working against very little resistance. As the pump has to lift the water higher or overcome more resistance through the discharge pipe or hose, the flow decreases.
At the pump's maximum head, the flow has effectively fallen to zero.
Your real operating point is somewhere between these two extremes and is determined by the pump curve and the resistance of your particular discharge arrangement.
That is why we recommend comparing pumps at the duty you actually need rather than choosing one purely because the number beside "litres per minute" is higher.
Manual flood pumps
If you will be present during a flood or clean-up, a manual puddle pump is often the simplest option. Manual operation also allows pumps designed for low-level drainage to continue removing water to their minimum pumping depth.
Best for smaller domestic floods: Stream SPP2-4
The Stream SPP2-4 is our starting point for smaller domestic floods and shallow water removal.
It is compact, lightweight and designed to clear standing water down to approximately 2mm. This makes it well suited to garages, utility rooms, cellars and smaller flooded areas where the water is clean or only slightly dirty.
Maximum head: 6m.
Maximum flow: 70 litres/min.
Low-level pumping: approximately 2mm.
Free passage: 3mm.
Best for heavier-duty flood response: Stream SPK530
For larger jobs and more demanding use, the Stream SPK530 is a heavier-duty puddle sucker used across residential, commercial, industrial and site applications.
It can pump standing water down to approximately 1mm under suitable conditions and has substantially more flow and head than the smaller SPP2-4.
It is also available in both 230V and 110V versions, making the 110V model suitable for applications where a compatible site supply is required.
Maximum head: 11m.
Maximum flow: 170 litres/min.
Low-level pumping: approximately 1mm.
Free passage: 5mm.
Best for higher-flow low-level pumping: EVAK Residox 400
The EVAK Residox 400 combines high flow with ultra-low-level pumping.
It has a stainless steel outer case, cast iron pump housing and is designed to remove standing water down to approximately 1mm. It is available in 110V and 230V versions and suits flood recovery, basement clearance and more demanding domestic or commercial applications.
Maximum head: 11m.
Maximum flow: 213 litres/min.
Low-level pumping: approximately 1mm.
Free passage: 2mm.
Automatic flood pumps
Automatic pumps make sense when the purpose is not simply to clear an existing flood, but to manage water as it arrives.
They can be useful in a cellar that fills following heavy rain, a property that is occasionally unoccupied, a commercial plant room or as part of a wider flood protection arrangement behind barriers or other defences.
A newer approach to low-level automatic flood pumping is a separate floor sensor. The sensor can sit at the point where water gathers first and switch the pump on before enough water has accumulated to operate a conventional tethered float switch.
We now use this arrangement on automatic versions of two of our most popular Stream puddle pumps.
Best compact automatic option: Stream SPP2-4A
The Stream SPP2-4A takes the compact SPP2-4 puddle pump and adds a separate automatic floor sensor.
The sensor starts the pump when water reaches approximately 20mm and switches it off at around 10mm. It is intended for applications such as domestic cellars, basements, garages and formed low points where shallow water can accumulate while nobody is there to operate a pump manually.
For normal plug-in operation there is no separate control panel or hardwiring required, although the electrical supply and installation must always be suitable for the environment in which the pump is being used.
Automatic start: approximately 20mm.
Automatic stop: approximately 10mm.
Maximum head: 6m.
Maximum flow: 70 litres/min.
Best heavy-duty automatic option: Stream SPK530A
The Stream SPK530A is the automatic version of the heavy-duty SPK530.
It combines the same 170 litre/min maximum flow and 11m maximum head with a separate floor sensor that starts the pump at approximately 20mm and stops it at approximately 10mm.
Its cast aluminium body, cast iron casing and 5mm free passage make it a more suitable option where greater flow, lift or durability is required, including commercial basements, plant rooms, lift pits and unattended dewatering duties.
Automatic start: approximately 20mm.
Automatic stop: approximately 10mm.
Maximum head: 11m.
Maximum flow: 170 litres/min.
Free passage: 5mm.
Best compact conventional automatic option: APP RS32EA
The APP RS32EA is a particularly compact automatic submersible pump. Its miniature float switch makes it useful where there is not enough room for a conventional tethered float to move freely.
That makes it a practical option for narrow sumps, confined cellar corners and other small drainage chambers.
Automatic start: approximately 50mm.
Automatic stop: approximately 25mm.
Maximum head: 7m.
Maximum flow: 130 litres/min.
Free passage: 4mm.
Adjustable low-level automatic control: EGO 500 SE LS
The EGO 500 SE LS uses electronic sensors rather than a conventional float switch.
It is factory set to switch on at approximately 125mm and off at around 40mm, but the levels are adjustable. The switch-on level can be reduced substantially and the off level can be set to just a few millimetres, giving more control over the water level than a traditional float-switch arrangement.
The pump continues operating briefly after the lower sensor is uncovered, allowing very low-level pumping. Where it is being left to operate automatically, the settings should be appropriate to the installation and should not cause unnecessary dry running or rapid cycling.
Maximum head: 7.5m.
Maximum flow: 170 litres/min.
Automatic levels: adjustable.
Best permanent domestic solution: FPS Iguazu Sump 635
A portable flood pump is not always the best answer.
Where flooding or groundwater ingress is recurrent, a permanently installed pump station can collect water at a defined low point and remove it automatically before it spreads across the floor.
The FPS Iguazu Sump 635 combines a 190 litre chamber with an automatic submersible drainage pump and internal pipework. It is commonly used for basements, garages, patios, gardens and as part of wider flood-resilience arrangements.
One of the main advantages is that the pump is already below floor level. Water flows towards the chamber and the pump operates automatically as the level rises.
Maximum head: 6.5m.
Maximum flow: 166 litres/min.
Operation: automatic packaged pump station.
See our full range of packaged pump stations for permanent and higher-capacity arrangements.
Do I need a dirty-water flood pump?
Possibly. "Floodwater" does not tell you how clean the water actually is.
Rainwater collecting inside a clean basement is very different from muddy surface water crossing a garden or water being removed from a flooded excavation.
Where the water contains significant silt, sand or debris, choose a pump with materials and an impeller suited to the duty and check its free passage.
A low-level puddle pump is excellent at removing shallow water from a floor, but that does not automatically make it the right pump for heavily contaminated water.
For water carrying silt, sand, grit or small soft solids, see our dirty-water pump range.
What if I need to move floodwater very quickly?
Large floods can require a different approach.
Where the priority is moving a very large volume of water rather than reducing the final water level to a few millimetres, a high-flow drainage or engine-driven pump may be more appropriate than a small puddle pump.
Our high-flow pump range includes submersible and engine-driven options for larger dewatering and flood-response duties.
Again, flow should be considered at the actual operating head rather than simply comparing maximum flow figures.
The pump is only part of the system
It is easy to concentrate on the pump and overlook everything downstream of it.
The hose diameter, hose construction, fittings, non-return valves and discharge route can make a major difference to how the pump performs.
A narrow hose increases friction. A long hose increases friction. Every bend and fitting adds resistance. Layflat hose can also kink when routed around steps or tight corners, potentially reducing or stopping the flow altogether.
A non-return valve can be particularly useful where water remains in the hose after the pump stops. Without one, part of that water may run back towards the pump.
This is why a correctly selected 70 litre/min pump with a sensible discharge arrangement can sometimes be more useful in practice than a much larger pump connected to an unsuitable length of undersized hose.
The easiest way to buy: a flood pump kit
A pump on its own is only half the job.
When flooding actually occurs, people often discover that the pump outlet does not match the hose they have, the layflat hose kinks on the cellar steps, the hose is too narrow, or water simply runs back down the line when the pump switches off.
The pump, hose, fittings and discharge arrangement need to work as a system.
That is why we created our FPS Engineered flood pump kits. Each kit combines a pump with matched components for a particular application, so you are buying a workable setup rather than a collection of unrelated parts.
- Domestic, manual: the Small Flood Pump Kit combines the SPP2-4 with reinforced 25mm hose and the fittings required for attended flood response in a garage, cellar, utility room or similar space.
- Domestic, automatic: the Automatic Home and Basement Flood Pump Kit combines the SPP2-4A floor-sensor pump with reinforced hose, fittings and a non-return valve for recurring shallow flooding.
- Commercial, automatic: the Automatic Commercial, Site and Plant Room Pump Kit uses the heavier-duty SPK530A where greater flow, lift and durability are required.
Using an electric flood pump safely
Floodwater and electricity can be a dangerous combination.
Do not enter floodwater to connect or operate electrical equipment where there may be an electrical hazard. If an electrical installation, socket, consumer unit, wiring or electrical equipment has been affected by flooding, obtain appropriate electrical advice before using mains-powered equipment in the affected area.
Government flood guidance also makes an important distinction between removing a relatively small amount of water and pumping a deeply flooded property.
Where large volumes of floodwater are being removed, the difference between the water level inside and outside a building can place pressure on the structure. Government guidance advises that pumping should begin when the outside water level is lower than the level inside. Where water in or around a property is around 1 metre deep or more, structural engineering advice should be sought.
If an electric pump forms part of a flood-protection system, also consider what happens if the electricity supply fails during the same storm. Depending on the risk, a high-water alarm, backup power arrangement or secondary pump may form part of a more resilient solution.
Fuel-powered pumps and generators introduce different risks. Generators and combustion engines produce carbon monoxide and must not be operated inside a building.
Where should a flood pump discharge?
A flood pump should discharge somewhere the water can get away safely without simply flowing back towards the building or creating flooding elsewhere.
The right point depends on the site and may include an appropriate drainage system, lower area or other approved discharge location.
Do not assume that you can automatically pump floodwater into a public sewer, highway drain, ditch or watercourse. Depending on the discharge point and circumstances, permission may be required from the relevant authority, water company or asset owner.
You should also consider whether the receiving drainage system is operating during the flood. Pumping into a sewer or drain that is already surcharging may achieve very little and can contribute to water returning towards the property.
Once a suitable discharge point has been identified, keep the hose route as short and unrestricted as reasonably practicable. Long hose runs, narrow diameters, bends and kinks all reduce pump performance.
Portable flood pump or permanent sump pump?
A portable pump makes sense where flooding is occasional, where the affected area changes, or where somebody will be present to deploy and supervise the equipment.
A permanent sump or pump station becomes more attractive where water repeatedly arrives at the same low point and needs to be dealt with automatically.
For example, a cellar that floods once every several years after an exceptional event may only justify a portable pump kept ready for deployment. A basement with regular groundwater ingress is a very different problem and may benefit from a properly designed permanent drainage and pumping system.
For more detail on this particular decision, read our cellar flooding water pump guide or browse our cellar and basement flooding pumps.
Choosing the right flood pump
If you only remember five things from this guide, remember these:
- Match the pump to the water. Clean, shallow water and muddy, debris-laden floodwater are different pumping duties.
- Decide how low you need to pump. A puddle pump is particularly useful where leaving several centimetres of water behind is not acceptable.
- Think about the actual flow you need. Maximum flow is not the flow you will necessarily achieve through your hose.
- Consider automatic operation before the flood happens. A manual pump cannot help if nobody is there to turn it on.
- Plan the whole discharge route. The pump, hose, fittings, head and discharge point all work together.
There is no single flood pump that is right for every situation. The aim is to select a pump that can manage the expected water, operate effectively against the required head and be deployed when it is actually needed.
If you are not sure where to start, use our Pump Finder or call the team on 0115 987 0358.
