I think it's fine, since it's watercooling (and I suppose you didn't overclock) it should be possible. Do know that temperature readings on CPU's are not always a 100% accurate in software and in BIOS it won't show temperatures under true load of the OS and programs.
CPU temp as measured how/in what application? (Try HWMonitor)
Even at idle, with the CPU running at only 800 MHz, I'd expect more than 19C, typically 26-27C or so...(If you had your PC in a 10C ambient area, perhaps 19C would be at least feasible)