i just discover a bug whit the xp shower on 1.5.1, so here is my set up, i got a drain on a tank and a xp shower on it, next to the shower is a lever (same result whit redstone torch) the lever is set to put the shower off, so i store my lvl in the tank and flip the lever when i need Xp. the thing is that on start up (starting the world) the shower ignore any redstone signal and empty the tank (lost 36 lvl of xp)