I'm no expert in this area (I watercool for quiet so I use low noise / low pressure pumps and tend to have no leakage) but I'd suggest you also mention the full details of your system. Stuff like pump type, tubing type, diameter, barb diameter, barb threaded portion sealed to water block or reservoir with what kind of sealant, anything else you can think of that might be relevant (don't bother posting the brand of your floppy drive
)
Don't forget that the water block itself might be leaking - particularly if you've ever had it disassembled.