Interface Drain : A pipe connection extending to the normal interface level with a vortex breaker which is used periodically to drain off any accumulated sludge. (Spec 12L)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}