i have a swiftech water system which has been running for about 6 months.it only cools the cpu and i have used distilled water.but i have noticed a drop in water level,is this normal.i have checked for leaks and cant see any.will i lose some water anyway.its about 5mm - 10mm.i have put a pencil mark on the reservoir and it has dropped in the past month,is this normal or u think i got slight leak somewhere.or shall i just top it back up.