Operating a pump wit a PIR sensor
A 2N7000 has too high a threshold voltage to reliably turn on completely with only 3.3V drive. 

You can drive your pump with a single MOSFET such as this one. 







simulate this circuit &ndash; Schematic created using CircuitLab

It's surface mount, but not scary lead pitch at all (TO-252). It will not require a heat sink if wired up correctly, and can switch on fully with 2.5V. Very few MOSFETs with low threshold voltage are available in through-hole packages (mostly older ones). They're around 50 cents in singles. R1 makes sure that Q1 switches off if the input is floating. D1 clamps any inductive transients from the pump motor.