Bilge pumps live in a hostile environment. On most boats they sit in at least a little saltwater and are expected to uncomplainingly pump water that may be contaminated with all sorts of detritus.
Many bilges are filthy. The worst culprits are often older, heavy-displacement sailboats with deep keel sumps. Their bilge pumps lurk at the bottom of these black holes, are never cleaned and are seldom inspected. Most boats often have at least two bilge pumps, sometimes three or four.
I have noticed that many sailors have come to rely totally on their electric pumps, which is a big mistake.
What if your batteries go flat, the pump burns out, or some other mishap causes the pump to stop working?
Don’t get me wrong, electric pumps are great, but surveyors like to see a manual diaphragm pump in addition to the electric pump. A manual pump can often move water faster than a small electric pump and is far less prone to clogging.
Many electric pumps have a separate float switch, which is a potential trouble spot. You should periodically check the operation of your float switch, as these do get hung up from time and a continuously running pump will soon flatten your battery. Another thing I often see are pumps that are not fixed in place and are merely held in position by their discharge hoses. I urge you to check the operation of your pumps regularly. The safety of your boat and crew may someday rely on them.