How They Work
It’s very simple really.
The pump is wired into a DC power supply. An electrical pressure switch in the pump is set to close or open at a certain PSI or pounds per square inch.
When a tap is opened the switch detects a pressure drop in the pipework and allows the pump to run. When the tap is closed, the pump runs for a few seconds to allow pressure to build up to a pre-set level in the pipework, at which the pressure switch turns the pump off.
It’s important to know the pressure parameters of your pump if you are to effectively use an accumulator tank. See our section on how to set up your accumulator elsewhere in this chapter.
Knowing that a pressure switch is fitted can help you to diagnose a problem in your water system.
If all the taps are closed and there are no drips from taps but the pump runs intermittently, say after a few hours of inactivity in the middle of the night, then you have a leak.
The leak may be the seals on the head of the pump itself, they do go after a few years. This is easy to check as it will be wet around the pump body. However, if all is dry at the pump and the taps are not leaking then water must be being lost at a joint somewhere.
Have a look in you access hatch in the cabin floor at the rear of your boat to see if there is evidence of water.
If you have no access hatch, you will just have to follow the runs of pipework until you find the leak. Make a note to get an access hatch cut!
Turn the pump off at the main fuse board if you are leaving the boat for a couple of days or more. Open a tap and relieve the pressure in the system. It’s kinder on seals and joints this way and it doesn’t take long for a pump to empty a water tank in the bilge if a leak occurs!
Installation requires reference to the manufacturers instructions but we can give you a general overview here.
Very occasionally you may run completely out of water. Despite having run-dry protection so as to not burn out the motor, it is standard practise to install the pump as close to the water tank as possible. This ensures that as it primes itself, seals are not damaged through over heating due to lack of lubrication. Mesh filter assemblies which connect directly to the inlet port of the pump are often a requirement of the warranty from the manufacturer. Fit one in any case as they will protect your expensive pump from damage from any large foreign objects that may have fallen into the tank. They are £5 well spent.
The pump should be mounted to a solid surface to minimise vibration.
Ensure any DC cable that you run to the pump is sized for suitability and voltage drop. See our section on Voltage Drop in the Electrical Chapter of our Product and Planning Guide.
Proven marine water pumps are readily available from all good chandlers