Federal law requires that all pool/spa drains that were manufactured distributed or sold on or after December 19, 2008 must meet ASME/ANSI A112.19.8-2007 requirements. In addition, all public pools and spas must be retrofitted with covers that meet the previous mentioned standards. Finally, all public pools and spas that have a single drain other than an unblockable drain must employ one or more SVRS device.
SVRS devices come in three main varieties:
1) Mechanical devices which let air into the circulation pump to ease the vacuum when entrapment or blockage is sensed by device.
2) Electro-mechanical devices which shut off circulation pump when entrapment or blockage is sensed.
3) Pumps or motors with built in software which shuts off circulation pump when entrapment or blockage is sensed.