Lithogen (my small business up in Canada - shameless plug) occasionally adds a cool tool to our rental fleet. We just added the RD510 acoustic pipe locator (great for plastic pipes!), which is a combination of a “water hammer” source and a single geophone. We’re still getting acquainted with it (so we can properly support it).

Here’s a short video I made showing off the water hammer. Officially Radiodetection Ltd says not to use it indoors, but I really wanted to see how it worked!