All guides · Keel and water
I would choose a bilge pump based on the specific installation and supplement it with an appropriate alarm plan. The pump's maximum flow rate alone does not tell you how much water actually comes out through the boat's hose routing.
Start with the bilge and the outlet
Note where the water collects, where the pump can be positioned, and how it can be reached for cleaning. Measure the height difference to the outlet and the total hose length. Look for narrow passages, bends, and places where the hose can form pockets.
Rule shows in their technical guide how unsuitable sags in the outlet hose can cause airlocks. The hose routing is therefore part of the pump selection. Use the specific pump's capacity data at the relevant delivery head and follow its installation manual.
| Selection | Questions before ordering |
|---|---|
| Pump | Does the voltage, performance, dimensions, and access for cleaning fit? |
| Outlet hose | Do the diameter, routing, and outlet location match the manual? |
| Automation | Built-in sensor or separate level switch, and how is it tested? |
| Level alarm | Where is an unusually high level detected, and where can the alarm be heard? |
| Power supply | Are the fuse, cables, and operation during normal harbor conditions planned? |
Automation and alarm have different tasks
The pump automation starts the pump under the conditions for which the model is designed. A high-water alarm is intended to alert you to a problem. I would consider a separate sensor and a solution where a single failure does not readily render both pumping and alerting ineffective.
If the pump is to be active when the boat is unmanned, it must have a documented, correctly fused power supply in that state. Have the installer clarify this; an automatic pump does not help if its power supply is inadvertently disconnected.
Check the entire chain
Plan a controlled functional test according to the manufacturer's instructions: sensor, start, actual discharge, and alarm. Hearing the motor run is not the same as seeing water being pumped out. Avoid a test that creates uncontrolled water ingress.
Maintain access and a backup plan
Clean and check according to the manual, and investigate the cause of new or unusual water in the boat. A bilge pump is not a repair for a leaking installation and provides no guarantee against major water ingress. Also, evaluate an appropriate manual or other independent dewatering option for the boat's use.
Sources and manufacturer documentation
Manufacturer documentation checked September 2026. Always follow the manual for the specific model and installation. The calculation examples are simplified examples for planning purposes.
Moving forward with your solution
Send the voltage, space requirements, hose dimensions, and height to the outlet, and I will help clarify a suitable pump.