Without proper bonding, a small stray electrical current (galvanic reaction) can be generated in a pool because of the presence of multiple types of metal, even when the pool is not running. This current must be controlled to meet new building codes and to prevent possible corrosive damage to those metal pool components. If the pool does not have proper bonding, or if you have replaced your pool lights which were previous providing the bonding source, a sacrificial zinc anode is a simple solution to protect the entire pool.
This zinc anode provides an easier path for galvanic reaction to be attracted to, protecting expensive metal pool components. The zinc anode is simple to replace when the inexpensive zinc anode is roughly half-eroded; the sacrificial zinc anode lasts approximately 3 years in most cases.
This item is not required by default when adding a salt chlorinator.