This is a fairly common issue, and one that is easily fixed. Much of it does depend on a few key points : 1 - That the pump is below the spigot level of the vessel you are pumping from, and that the tubing isn't excessively long below the spigot level. As these pumps are designed to push the liquid, it does not pull or self prime. Pump placement is important for these types of non-self-priming pumps. 2 - All the ports and tubing to the inlet of the pump are 1/2" I.D. There may be some situations where a port is only 3/8", but the tubing should not be. 3 - All ball valves in line are fully open when starting the pump. If these three criteria are met and you are having cavitation issues in warm/hot fluids then try this. Either set up a switch inline from your pump to the socket, or quickly unplug your pump and plug it back in again after waiting about 60 seconds. If you have a switch, simply turn it on and then off again instantly. What we are doing is turning the impeller head, so each section of the impellor can allow the liquid inside the pump head to push out any air that might be stuck in there. If you do this 3 times very quickly, you should be able to give it full power after that, and have full flow.