Minimally invasive mitral valve repair has become standard. We hypothesized that reproducible water testing with less air contaminations may help achieve successful repair and prevent air embolism. We used a long shaft irrigation device connected to an infuser pump to water test mitral valve repair in 104 consecutive patients with severe mitral regurgitation due to type II mitral valve dysfunction. All patients underwent mitral valve repair via small right thoracotomy. Water testing was performed by simultaneously monitoring root pressure to confirm valve competence and adequate leaflet coaptation with suitable pressure. Irrigation was stopped when root pressure reached 60 mm Hg. Simultaneous transesophageal echocardiography showed a negligible amount of air introduction. Predischarge echocardiography revealed residual mitral regurgitation of less than or equal to 1 in all patients, and no patient experienced any major adverse event such as stroke or perioperative myocardial infarction. This novel water test allowed us to correctly check mitral valve competence and reduce air contamination.