Well if bacteriostatic water is adjusted to physiological osmolarity, every bit of salt you add will increase the osmolarity past the physiological level. At twice this level (300->600mOsm/L) tissue damage will occur. Definitely at 900mOsm/L, but often at 600. Check if it says 0.9% NaCl on there and if it does, use tap water instead. That is if you use 200nm micron filters ofc!!