Help with base resistor (and transistor selection?)

It's not Very Bad. The question is what is most common: float switch is closed or float switch is open? If the float switch is closed 99% of the time then you are wasting current through the path 5V --> 220 ohms --> float switch closed --> ground. As long as you don't mind wasting this current then it's OK.

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Beat707: MIDI drum machine / sequencer / groove-box for Arduino