Setting up a Dredge

To begin with, when an engine is first started the impellers force almost all the air out into the high pressure tube and here it is slightly compressed. Any air from the intake hose is also pulled out and helps a little to raise the water inside the intake hose. This amount of this air is very small and only consists of a fraction of a cubic foot. The water that is rushing in covers all the air and lets it out with the first surge of water through the pressure hose.

Another point is that after the pump begins to open it obtains its maximum capacity very quickly and the pressure is very high and this is why it is called a high pressure hose. If you loosen the hose at the pump, the pressure can cause it to slip easily and come off and it is almost impossible to install it again. If you loosen the hose at the injector, the pressure has a tendency of straightening the hose out and bending it back to connect it again can be quite a hassle. Whatever the case, if it does so happen to come loose, know for sure that you are going to get plenty wet.

When the pump is evacuating the air naturally from its system you should be able to see in the clear plastic hose turbulence that is normally in the form of little bubbles. It is not very likely the entrained air will form into a consolidated mass of compressed air that will resist the flow of the water. If this did not happen the water around the mass would be at vapor pressure and would take over the air pocket and it would cause cavitation.

If cavitation were to happen in the high pressure hose the big mass of compressed air would alternately fall and come back as one ore more little masses so many times per minute that it would not even be seen. What would occur is that you would be able to see the little bubbles that are moving down the current flow quick quickly. This is pretty common inside the high pressure hose when the flow is just beginning.