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Home » Product & Planning Guide » Integral Parts » Bilge Pumps on
Narrowboats & Canal Boats


A vital piece of safety equipment, your canal boat will have a bilge pump fitted in the engine compartment.

Here we look at what a bilge is and why it may be good practice to fit more than one pump.

Where's your bilge!
The bilge is the lowest area in the boat. Basically the whole area directly above the base plate from bow to stern, below sub floors and engine.

Reference is usually given only to the area directly underneath the propeller shaft in the stern, but it is important to remember the cabin bilge.

Where to place your bilge pumps.
Bilge pumps should be fitted where ever this total bilge area is divided by a solid bulkhead.

Accumulation of water in the engine compartment can come from condensation, a leaking cooling system, a poorly sealed weed hatch, rainwater and, importantly, from the propeller shaft outlet (stern gland).
Collection of water in the cabin bilge can come from condensation, leaking water pipes, bath, sink and shower outlets or even leaking windows. We know of one boat whose washing machine outlet was plumbed into the cabin bilge. The owner became aware when the bilge pump failed and the dirty, soapy water filled the bottom of the boat!
Basically, anywhere water can leak into your canal boat it will!

We also know of several owners who had no idea of water collecting in their cabin bilge until the boat was hauled out on an angled slipway and water rushed out from the bases of cupboards. Not healthy or ideal living conditions we think, but sometimes ignorance can be bliss for some!

Canal boats are designed such that any water that gets into the cabin bilge will drain down towards the rear. Some have an open bilge that runs straight into the engine bay. Others have a wooden, now usually steel, bulkhead that separates the cabin bilge from the engine bilge.
If your boat has a separate cabin and engine bilge you should ideally install a bilge pump in the cabin bilge against the rearmost bulkhead plus one in the engine compartment.

Bilge pumps in the engine compartment are usually sited in a bund area under the propeller shaft. It is quite likely that this bund, or contained area, is separated from the area under the engine by a small steel plate. This is simply to ensure that any water dripping from the stern gland is contained in the bunded area and collected by the bilge pump rather than flowing across the engine bay.

If you are concerned about water entering the under-engine area, say from rain on deck boards in winter or because you have a raw water cooling system, then consider fitting another pump in this area. In practise, with regular maintenance and attention, this should not really be necessary.

Hand, manual electric, automatic electric...
There are various types of pump available from all good chandlers. The most basic type of pump is hand operated. Electrically operated bilge pumps require either a manual switch to operate or are fully automatic.

Installation follows the manufacturers guidance, but again, if you are unsure follow our advice for cable specification. Pay particular attention to the rating of the outside cable insulation as bilges are harsh places.

If the pump is automatic, i.e it uses a float to activate the motor, then wire it so that it is always on. There is no point in having an automatic pump that doesn’t work when you’re not there! The Law of Slowly Sinking Canal Boats dictates that you will really need your bilge pump to work when you're not aboard, or able to be attentive.

Incidentally, bypassing of battery isolation switches by bilge pump installations is one of the few allowable exceptions of the Boat Safety Scheme. It makes sense that either the manual switch or the pump itself can be operated if the batteries have been isolated from the main engine or habitation systems. Your examiner will check your wiring so do it in accordance with the BSS.
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