This week I was able to test the water flow meter I got from Adafruit. Here's a link to the code if you want to check it out: newLeak.asm
Unfortunately, the flow meter only starts registering at about 80 ticks per second, which I think is too much for a slow leak.
So I decided to play around with sensing vibration from a leak using a piezo buzzer. Here is the code I adapted from Elliot Williams 'Foot Detector' program in AVR-Programming. piezoLeak.asm Interesting data to play with.