Also Known As: Safety Vacuum Release Systems
If a drain cover becomes blocked, the pump will continue to pull water from the pool, creating suction. The blockage cannot be released and anything near the main drain can be trapped, potentially causing injury or drowning. An SVRS releases the entrapment, before suction becomes too powerful and dangerous.
There are two kinds of SVRS products. One provides an opening in the plumbing line, which reduces pressure in the case of an entrapment and releases the blockage. The second turns off the pump, if the lines are blocked, preventing suction. For both types, its important that the lines do not have a check valve that prevents the vacuum from being released. In addition, a hydrostatic relief valve can affect how the SVRS works.
The Virginia Graeme Baker Act requires that an SVRS be installed on all single-drain commercial pools. Pool owners and managers should be familiar with this regulation to be sure that they are meeting it and keeping swimmers safe.