Pool Safety Vaccum Release System 01.20.2011 Pool Safety Vacuum Release System :The recalled product is a black plastic device that screws into the drain hole of a swimming pool or spa circulation pump. As part of the circulation systems, the device is designed to release the vacuum in a drain line whenever a submerged drain cover of a swimming pool or spa is completely covered.
http://www.cpsc.gov/cpscpub/prerel/prhtml11/11101.html
