Vent valve used on underground and low volume aboveground tanks for motor fueling. Vent allows tank to “breathe” during filling and discharging operations. Poppets seal vapors in the tanks when pressure is equalized. Settings are approximate. Warning: Fig. 749 P/V vent must only be used in conjunction with motor fueling and/or low capacity flow. Fluid handling in lines larger than that used for retail service stations can cause tank to rupture or implode.