My brother plays trombone. He had just started learning when one day he operated the spit valve and nothing came out! Never thinking that this was because there wasn't any spit in there he decided, all on his own, that it was plugged. Sure, music (or something similar) came out when he played but there was no spit!

So he took it into the yard and, bell end up, filled it with water and then poured in a drain opening chemical.

First, this did the trombone no good at all and second, it didn't reach the spit valve area. So he simply kept pouring in the water until it overflowed from the bell. Then he reversed the instrument and did the same thing via the mouthpiece. He drained it through the spit valve, taking the cork seal off it at the same time.

Drain cleaners don't mix well with the finish or the innards of trombones. They don't improve the tone or anything else about them.

Fortunately it was a very old and very used trombone Mother had bought at an auction for a very few dollars.

My brother went on to finish his trombonic education with an instrument borrowed from the school -- and while it's difficult to believe he actually became a fairly decent trombonist. He also learned the correct way to clean a trombone and that a lack of spit is not a problem as long as there's no lack of music coming out.