This causes other problems though.
Vampires will prefer to drink booze from the stockpile to maintain their cover identity, rather than drink nasty well water. (Even if it does taste like delicious dwarf.)
It has been reported that they will purposefully reduce their efficiency to suit the cover story if burrowed, and forced to drink water instead.
So, either we purposefully reduce their efficiency (isn't this why we are trying to integrate them safely into dwarven society in the first place?) To keep them from eatuing urist McCatlady's 15 worthless children and creating a tantrum spiral, or we keep the efficiency, and risk said spiral...
Proposed experiment:
Part 1: determine if booze can contaminate a well. (Drop a barrel from a very high place into the well, destroying it and spilling the contents inside?)
Part 2: should a well be so contaminated, does the watered down booze satisfy the booze dependency?
If both conditions are true, dropping all three of the source vampire, the normal dwarf, and the barrel of booze into the bloodletting trap should have 3 noteworthy effects.
1) dwarves drinking the nasty water will only have a bad thought, but won't experience a loss of performance associated with withdrawl.
2) dwarves who drink the nasty water will become vampires, boosting their stats.
3) vampires trying to hide that they became vampires will be sated by the normal dwarf blood in the water, preventing uncontrolled feeding.
I do not have any vampires, so I cannot fully perform this experiment.