Chris; I wonder about the make and model of your horn, its age general condition, etc. to determine if a valve rebuild,( including replate ) is economically feasable. More info please.
I am the owner and player of a rather healthy sized stable of vintage trumpets and cornets, so I am familiar with your problem. The advice to first thoroughly clean and dry your horn and its valves is valid advice. Use of a thicker valve oil is another trick to seal up leaky valves. It does make the valves slightly sluggish, though. If it is deemed economically feasable and that no other remedy exists for your valves, contact David Williams
Thebrassmaster@earthlink.net or 850-224-9909.Dave does total valve rebuilds and alignments for $200.00 for all three valves, complete,+ $25.00 for packaging and return shipping. Dave does fine work and is currently rebuilding the valves of my prized and rare York Master Model trumpet.
OLDLOU>>