Overview Reviews Product Description The 500AV and 525AV are pressure and vacuum relief caps for farm and industrial storage tanks featuring NPT threaded valves.The lockable cap rotates to control gravity flow from above ground storage tanks (padlock not included). Greenline Industrial Fitting Catalog New Greenline Industrial Fitting Catalog Product Videos Custom Field Product Reviews Write a Review Write a Review × Greenline 1-1/4" NPT Lockable Angle Valve 525AV Rating * Select Rating 1 star (worst) 2 stars 3 stars (average) 4 stars 5 stars (best) Name Review Subject * Comments *