Can I caulk a hose connection for a pool vacuum pump?
Caulking is designed to keep water out of cracks.  It remains relatively soft and pliable even after it sets up so that vibrations do not cause it to crack. One thing it does not have is great adhesion properties. If you've ever started peeling it you will know what I mean - it pulls off relatively easily.  Because of this, I doubt it will hold up to water pressure in a pipe.

The connection type will determine how you should connect this.  If it is a push-on barbed connection then you can use a pipe clamp around the connection to tighten it up.



If it is a threaded connection then you can use teflon tape or pipe dope.  If it is a glued connection then likely you did not glue it correctly and you will need to re-do it.