EVAK Residox 400 Automatic Puddle Pump with Crab Sensor | Low-Level, 205 L/min

EVAK Residox 400 Automatic Puddle Pump | Crab Sensor for Low-Level Pumping | 230V

The EVAK Residox 400 Automatic combines the Residox 400 puddle pump with EVAK's Crab Sensor, an integrated floor-level electronic sensor, for unattended low-level pumping in basements, sump pits, lift shafts, plant rooms and any defined area where water periodically collects.

Why this is preferable to a float switch

Most automatic drainage pumps use a tethered float switch, which requires several centimetres of water to swing freely. Float switches are not well suited to puddle-pumping, where the objective is to remove water down to floor level. The Residox Automatic uses the Crab Sensor instead: a small, weighted electronic probe (in effect a floor-level float switch with no moving float), hard-wired into the pump, which sits flat on the ground next to it. The probe detects water at 3 mm (±1 mm) above floor level, well below the level any pendant float switch could reach.

Note that the operating cycle of this automatic pump is governed by the sensor, not the pump itself. The Residox 400 is mechanically capable of pumping water down to approximately 1 mm above the floor (as in the manual version), but in automatic operation the sensor will signal the pump to stop once the water level falls below the 3 mm trigger point. For jobs requiring water to be removed to the lowest possible level in a single pass, the manual Residox 400 is the more appropriate choice.

Plug in and run, no control panel required

The sensor is wired into the pump as a single unit, so no control panel, piggyback plug or external wiring is required. The pump plugs into a standard 230V mains socket and the sensor controls operation. Both the pump and the sensor probe are rated IP68 and fully submersible.

The automatic version is only available in 230V.

Adjustable Sensor Delay

The two delay times are one of the most significant practical advantages of this pump over float-switch alternatives.

The start delay (factory setting 5 seconds) requires the sensor to detect water continuously for the duration of the delay before the pump activates. Brief water events such as a splash, a momentary drip, or run-off from cleaning will dissipate before the delay expires, and the pump will not start. This prevents unnecessary cycling and reduces motor wear from reacting to non-events.

The stop delay (factory setting 30 seconds) keeps the pump running for the duration of the delay after the water level has fallen below the sensor. Without this delay, the pump would shut off the moment the water cleared the sensor and immediately restart as more water entered, producing a high frequency of short on/off cycles. Rapid cycling is one of the most common causes of premature motor failure in automatic pumps. The stop delay allows the pump to complete each pumping cycle fully before resting.

Both delays are adjustable from 1 to 120 seconds using the supplied magnetic key, held against the side of the sensor housing.

Important: do not run dry

Setting the stop delay too long will leave the pump running after the water has cleared, which damages the seals and shortens motor life. The factory 30-second setting is suitable for most installations. Increase the stop delay only when the pump has demonstrably more water to clear at that point in the cycle. 

It should be set to suit the operating environment.

Suitable applications

•    Basements, cellars and lift shafts with known water-ingress problems
•    Plant rooms and utility areas where unmonitored leaks pose a flood risk
•    Sump pits that fill periodically and require draining without a permanent float
•    Facilities management sites where attending every drain-down is impractical
•    Permanent passive flood defence

Less suitable for

Fast-flowing, turbulent or intermittent water (such as surface rainwater in an exposed area) can cause excessive cycling even with the delays in place. In these situations, the manual Residox or a system with additional level controls is more appropriate.

Build and capacity

The Residox 400 Automatic shares the manual model's build standard: cast iron pump housing, stainless steel outer case and handle, Hytrel vortex impeller, 2 mm free passage, and rubberised NBR base. The pump delivers up to 205 litres per minute with an 11-metre head. No priming is required (unlike a Tsurumi LSC, which needs water poured in before first use).

The automatic version is supplied as a 230V unit only. For 110V site use, the manual Residox 400 with a separately fitted control system is the appropriate alternative.

Specification

Key Features

✔ Crab Sensor: integrated floor-level sensor, hard-wired into the pump 
✔ Detects water at 3 mm (±1 mm) above floor 
✔ Adjustable delays prevent rapid on/off cycling, protecting the motor 
✔ Start delay 1 to 120 seconds (factory 5) 
✔ Stop delay 1 to 120 seconds (factory 30) 
✔ Plug straight into 230V mains, no control panel required 
✔ Pump and sensor both rated IP68 
✔ Full Residox build: cast iron, stainless steel, Hytrel impeller 
✔ 205 l/min flow, 11 m head, 2 mm free passage 
✔ 230V only, 1-year manufacturer's warranty

What's in the Box

✅ 1 x EVAK Residox 400 Automatic Puddle Pump with integrated Crab Sensor 
✅ 1 x Magnetic key for delay-time adjustment 
✅ 1 x 10m heavy-duty rubber power cable 
✅ 1 x 2 inch (50mm) hose tail

Optional: add a 90° elbow hose tail to prevent hose kinking and maintain optimum flow.