Johny Apple Bomb
im sorry, but what do you mean by runaway current?
Distilled water is a poor conductor. As more silver gets in the water the conductivity goes up. When you get to 10 ppm the current increases to much (unless you have a current limiter circuit) and this causes larger particles to break off the silver rods.
and is 10ppm bad...?
10 ppm is fine. If you go above 20 ppm quality drops due to agglomeration. Any lower than 5 ppm is to low. I like it at 20 ppm.