I recently used this to find a suction side leak that plagued me for 7 years.... Start with each joint or in my case it turned out to be an o-ring on the cap on the manifold that I use to blow out the pipes for the winter.. was totally rotted. I started with each joint and put shaving cream all around it. Watch and when you hear the pump suck air see if you can see any bubbles in the shaving cream. It clearly sucked in the shaving cream when it sucked in the air. Worked great!!! 7 years I couldnt find that stupid leak.... Of course I never even thought to look at that stupid o-ring before!!!! Good luck!!!!