Description The OPW 71SO-420C Overfill Prevention Valve is designed to prevent the overfill of underground storage tanks by providing a positive shut-off of product delivery. Key Features Simple, Easy and Quick Installation - No excavation or special manholes required. Economical - Costs a fraction of expensive, complicated and difficult-to-install valves. Furnished Coplete - Supplied with new upper and lower drop tubes, mounting hardware and thorough instructions for quick job site time. Completely Automatic Operation - No pre-checks to perform, no resets, and no overrides to be broken or abused. No Pressurization of the Tank - Operates directly from liquid level. Will Accept a Dipstick for Gauging. Retrofits Directly - For both new and existing tanks with 4" fill risers. Quick Drain Feature - Automatically drains hose when head pressure is relieved. *This item is not eligible for free shipping.