I call dibs on What is a spit valve? A spit valve is a tool you use to put on a instrument. It collects the water that comes out of your mouth. It also helps the instument that you're using it for. Some of those instuments you can use it for are Trumpets, and Trombones, clairnet, saxaphone. The water key or spit valve is a small hole that's usuaslly closed. Pressing the water key opens the small hole, allowing the water to empty. Here are the wonder words are alto, soprano, and last but not least valve. lIf you want to go and see some morefacts click the link below.