J. Over Pressure Valve (OPV) on the Exhalation Counter lung

MX Rebreather - Over Pressure Valve (OPV) on the Exhalation Counter lung

The over pressure relief valve, or OPV, is mounted on the bottom inside of the exhalation counter lung. This OPV releases excessive gas volume if built up in the counterlung. It is mounted on the inside bottom of the counter lung, so the diver can reach it with their left hand and pull the dump string if needed. This action can also be done when the diver wants to dump any water that is trapped in the exhalation pontoon. Essentially the OPV acts as the water dump valve from the exhalation counter lung. Keep in mind that we dive in the prone position, so it would require a slight rolling to the left side and raising of the divers head, while pulling the dump string with the left hand and dil flushing with the right. Sounds more difficult than it is to dump the water.