An in-depth description of what cavitation is, how cavitation can occur in pumps, how to prevent pump cavitation, and the effects pump cavitation can have on your pump. Pump cavitation is very noticeable and can cause serious damage to your pump, so it's important to be able to identify and diagnose cavitation whenever it occurs.

Cavitation is the formation of bubbles when the pressure in certain spots of a pump begins to reach the vapor pressure of the fluid inside. When the pressure inside the pump gets as low as or lower than the vapor pressure of the fluid, the fluid begins to evaporate, creating bubbles. These bubbles exist until they reach a higher pressure area.

Pump cavitation is generally found in the inlet of pumps or in narrow piping sections, which are the areas that will have the lowest pressure in the pump. This is most pronounced around the edges of any inlet in the pump. The bubbles formed by these low pressure areas quickly reach an area pressurized enough to turn them back into water. Due to the properties of water when pressurized, when the bubbles pop they emit a powerful pressure shock. The volume of bubbles and shocks creates a loud noise.

The reason cavitation can be damaging comes from how each bubble collapses. Rather than the pressure shock damaging the pump, a small stream of water is expelled from the center of the bubble, and is powerful enough to cause micro cracks in material. Over time, this effect builds up, so much so that the pump can be seriously damaged. This small stream of water, called a micro jet, is formed by the way the bubble explodes - or more precisely, implodes.

Each cavitation bubble implodes upon itself, with the leading edge pushing back towards the opposite end of the bubble. Essentially, when the two edges make contact, they open up a hole in the bubble, and the force of the two edges connecting drags water through the newly-formed hole and launches the micro jet of fluid directly out. The micro-cracks caused by this are not immediately serious, but over the course of several months to a few years, cavitation can seriously damage the pump.