The EVAK Residox is an ultra-low-level puddle pump built by EVAK, capable of removing standing water down to approximately 1 mm above floor level. The range covers two flow capacities, the 400 and the 750, each available in a manual vers...
The EVAK Residox is an ultra-low-level puddle pump built by EVAK, capable of removing standing water down to approximately 1 mm above floor level. The range covers two flow capacities, the 400 and the 750, each available in a manual version (operator-controlled, 110V or 230V) and an automatic version with an integrated crab sensor (230V only). Choose by flow rate first, then by whether you want manual control or unattended operation.
All four pumps share the same build standard: cast iron pump housing, stainless steel outer case and handle, alloy motor and seal casing, Hytrel vortex impeller, 2 mm free passage and a rubberised NBR base that sits flush on tiles, finished concrete and other surfaces without causing damage. They differ only in flow capacity, head and how the pump is started and stopped.
Comparison at a Glance
EVAK Residox 400 Manual
The standard model. 250 litres per minute and 11 metres of head, available in either 110V (for site use with a transformer) or 230V (domestic and general purpose). Suited to most domestic and commercial flood-recovery jobs, basement clearance, internal floor drainage and general nuisance water. Operator controlled, manual pump.
EVAK Residox 750 Manual
The higher-output model. 330 litres per minute and 16 metres of head, available in 110V or 230V. The 750 is the appropriate choice when the area is larger, the hose run is longer, or the discharge point is uphill of the water source. Operation is identical to the 400 manual, turned off and on at the plug.
EVAK Residox 400 Automatic
The Residox 400 fitted with an integrated crab sensor. The sensor sits flat on the ground next to the pump on its short metal prongs, detects water at approximately 3 mm above floor level, and signals the pump to start and stop automatically. Adjustable start and stop delays prevent rapid on/off cycling, which is the most common cause of motor failure in float-switch automatic pumps. Suited to basements, lift shafts, plant rooms, sump pits and any location where unattended drainage is needed. 230V only.
EVAK Residox 750 Automatic
The same crab sensor system fitted to the higher-output 750 pump. The choice when an unattended installation needs to handle larger volumes or higher discharge heads than the 400 can deliver. 230V only.
The deeper read: what's in this range, how to pick, and when to talk to us before you buy.
| Model | Flow | Head | Voltage | Operation |
|---|---|---|---|---|
| Residox 400 Manual | 250 l/min | 11 m | 110V or 230V | Manual |
| Residox 750 Manual | 330 l/min | 16 m | 110V or 230V | Manual |
| Residox 400 Automatic | 250 l/min | 11 m | 230V only | Automatic, integrated crab sensor |
| Residox 750 Automatic | 330 l/min | 16 m | 230V only | Automatic, integrated crab sensor |
EVAK Residox 400 Manual
The standard model. 250 litres per minute and 11 metres of head, available in either 110V (for site use with a transformer) or 230V (domestic and general purpose). Suited to most domestic and commercial flood-recovery jobs, basement clearance, internal floor drainage and general nuisance water. Operator controlled, manual pump.
EVAK Residox 750 Manual
The higher-output model. 330 litres per minute and 16 metres of head, available in 110V or 230V. The 750 is the appropriate choice when the area is larger, the hose run is longer, or the discharge point is uphill of the water source. Operation is identical to the 400 manual, turned off and on at the plug.
EVAK Residox 400 Automatic
The Residox 400 fitted with an integrated crab sensor. The sensor sits flat on the ground next to the pump on its short metal prongs, detects water at approximately 3 mm above floor level, and signals the pump to start and stop automatically. Adjustable start and stop delays prevent rapid on/off cycling, which is the most common cause of motor failure in float-switch automatic pumps. Suited to basements, lift shafts, plant rooms, sump pits and any location where unattended drainage is needed. 230V only.
EVAK Residox 750 Automatic
The same crab sensor system fitted to the higher-output 750 pump. The choice when an unattended installation needs to handle larger volumes or higher discharge heads than the 400 can deliver. 230V only.
For a real-world example of the Residox 400 in service, see our case study on using an EVAK Residox puddle pump behind a flood barrier. The pump was deployed on a driveway behind a Water-Gate flood barrier during a flash flood event, managing seepage that no flood defence can fully prevent. The case study covers pump positioning, hose selection, and why a portable manual puddle pump was the right choice for short-duration flooding, where a packaged pump station would normally be preferred for longer events.
The decision is determined by how the pump will be used.
A manual Residox is the right choice when the user is present, when the goal is to remove water down to the lowest possible level in a single pass, and when the available power supply may be 110V or 230V. Typical applications are attended flood response, controlled site work, basement and floor drying, and hire-fleet use.
An automatic Residox is the right choice when the pump needs to operate without an operator present, in a defined area where water periodically collects. The crab sensor will signal the pump to stop once the water falls below approximately 3 mm above the floor, which is well below the level any tethered float switch could reach but above the 1 mm capability of the manual model. Typical applications are basements with known ingress, lift shafts, plant rooms and sump pits.
The Automatic Version | An FPS Initiative
The automatic Residox was added to the range by Flood and Water Pumps in response to repeated requests from customers needing an unattended low-level pump that did not rely on a tethered float switch. We worked with EVAK to bring the model to market, built around the crab sensor: a small electronic probe, hard-wired into the pump, that sits flat on the floor on short metal prongs and triggers at water level. The result is a single plug-and-go unit that requires no control panel and no separate float, with adjustable delays to prevent the rapid cycling that shortens the life of conventional automatic puddle pumps.
Why the Crab Sensor Matters
The crab sensor is a type of float switch, but it works on an entirely different principle to the conventional tethered float used on most automatic drainage pumps. A tethered float needs several centimetres of water to swing freely, which makes it poorly suited to puddle pumping where the objective is to remove water as close to floor level as possible. The crab sensor instead sits flat on the ground and detects water electronically at 3 mm (±1 mm) above floor level. Both the pump and the sensor are rated IP68 and fully submersible.
Voltage and Compatibility
The manual Residox 400 and 750 are available in either 110V (for site use with a transformer) or 230V (domestic and general purpose). The automatic Residox 400 and 750 are available in 230V only. For a 110V automatic installation, the standard approach is to use the manual Residox with an external level-control system.
Flow rate and head. The Residox 400 delivers 250 l/min with an 11 m head. The Residox 750 delivers 330 l/min with a 16 m head.
Both pumps share the same build, free passage and ultra-low-level capability. The 750 is the appropriate choice for larger areas, longer hose runs or uphill discharge.
The manual version is started and stopped by the operator and can pump down to approximately 1 mm above the floor. The automatic version has an integrated crab sensor that starts and stops the pump at approximately 3 mm above the floor, allowing unattended operation in basements, sump pits and similar locations.
A crab sensor is a type of float switch that sits flat on the floor on short metal prongs, detecting water electronically rather than by the buoyancy of a swinging float. It triggers at approximately 3 mm above floor level, which is far lower than any pendant float switch can reach. The name comes from the way the sensor sits flush on the ground on its prongs.
No. The automatic Residox 400 and Residox 750 are 230V only. The manual Residox is available in either 110V or 230V.
The pump and crab sensor are rated IP68 and fully submersible. However, fast-flowing or turbulent water can cause excessive cycling or move/disturb the float switch.
No. Unlike some other ultra-low-level pumps such as the Tsurumi LSC range, the Residox does not require water to be poured into the pump body before use. Place it down and switch it on.
No. The crab sensor is hard-wired into the pump and the unit plugs straight into a standard 230V mains socket. No control panel, piggyback plug or external wiring is required.
The Residox is manufactured by EVAK. The automatic version was developed in collaboration with Flood and Water Pumps, who specified the crab sensor approach as an alternative to pendant float switches or the manual option.
