Sterile water
Sterile water is water that has been sterilised and contains nothing else. Once the stopper is entered, anything introduced can grow, so it is treated as single-entry and the remainder discarded.
Bacteriostatic water
Bacteriostatic water contains 0.9% benzyl alcohol, which inhibits bacterial growth. That allows the vial to be entered more than once within a defined in-use period, counted from first entry rather than from when the outer packaging was opened.
Bacteriostatic does not mean sterilising. It inhibits growth; it does not eliminate contamination already introduced.
Choosing between them
The compound decides. Some peptides are incompatible with benzyl alcohol, and for those the preservative is a liability rather than a convenience. Compatibility is stated per compound in its documentation.
Storage
Bacteriostatic water is stored at room temperature and does not need refrigeration. Its in-use limit relates to preservative effectiveness, not to the water.
Research use only. This page is explanatory and does not recommend any use, quantity or procedure. REVIVE LAB supplies reference materials for laboratory research. These are not medicines and are not for human or veterinary consumption. Anyone considering the use of any compound in humans should do so only under qualified medical supervision.