Test it now
The in-game test may not have the same configuration you want, check the configuration to see what else you can do.
To test the script, bring up the "polmav" vehicle via the /car polmav or from the F1 menu, then type in the chat /setupbucket
You can start a fire by typing /startfire normal2 5 1
Place the bucket in the water and wait for the liters to fill up
To delete the bucket, you can either delete the helicopter, via a /dv or go to the bucket and follow the instructions.