Instructions on Setting up your Dredge

On almost all dredges the pump intake hose is loaded with a foot valve and strainer. These are normally butterfly type valves that open when pressure is placed on the bottom side and it will then close when pressure is no longer there. The tension on the valve is not high and is just enough to close it.

In order to prime the centrifugal pump you will need to move the end of the pump intake hose quickly up and down under the surface of the water. With each stroke the foot valve will open and will allow the water to flow into the pump intake hose. With each stroke the water is also trapped inside the hose when the butterfly valve closes.

The water that has been trapped on the inside of the hose has a little bit of a momentum and has a tendency of remaining there during the following stroke and this creates a small low pressure area that increases the speed intake of the water while the butterfly valve opens. When this is moved up and down in this way the foot valve is like a small piston pump that forces the water up the intake hose in a very efficient way. To prime the centrifugal pump this has to push the water up around one or two feet and this does not require a great deal of effort.

After the priming water goes into the pump, the impellers push it outwards towards the pump housing very rapidly and this creates another low pressure area that pulls the water inside the intake hose to the impellers with a lot more momentum. This make the foot valve to stay open and water is constantly flowing to the impellers. While it may seem like a big explanation, in actuality the whole process only takes a few seconds, we are only describing what goes on inside.

Something that a lot of people just starting out do by mistake is not make the up and down thrusts quick enough so the momentum of the water in the intake tube can do what it needs to do. Move the foot valve quickly enough and the surge of water through the pump will happen so fast that you may be surprised.

The biggest problem that can occur when priming the pump is the air that is contained inside the pump and high pressure hose. The air needs to be evacuated and is usually packed together.