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Overfill Prevention Valve for UST

The CARB-certified OPW 71SO vapor-tight Overfill Prevention Valve is designed to prevent the overfill of underground storage tanks by providing a positive shut-off of product delivery. The shut-off valve is an integral part of the drop tube used for gravity filling. The OPW 71SO allows easy installation (without breaking concrete) and requires no special manholes.

The OPW 71SO is a vapor-tight two-stage shut-off valve. When the liquid level rises to about 95% of tank capacity, the valve mechanism is released, closing automatically with the flow. This reduces the flow rate to approximately 5 gpm through a bypass valve. The operator may then stop the filling process and disconnect and drain the delivery hose. As long as the liquid exceeds the 95% level, the valve will close automatically each time delivery is attempted.

If the delivery is not stopped and the liquid rises to about 98% of tank capacity, the bypass valve closes completely. No additional liquid can flow into the tank until the level drops below a reset point.


  • Valve Body: Cast aluminum
  • Float: Nitrile rubber, closed cell foam
  • Valve: Aluminum
  • Seals: Viton®
  • Upper & lower drop tube: Aluminum
  • Plastic parts: Acetal
  • Hardware: Stainless steel

Advantages of Overfill Prevention Compared to Overfill Warning Systems:

  • Completely Automatic Operation – does not rely on the alertness or speed of response of the delivery attendant for certainty of overfill prevention.
  • Keeps the Top of UST “Dry,” per EPA Requirements – eliminating possible leaks at loose bung fittings and the need for double containment on vent lines.
  • Does Not Rely on Pressure in the UST to Stop Flow – allowing faster fill times and reducing spill risk.
  • Speeds Delivery Operations – product flows unimpeded into the tank until the hose “kick” that accompanies the valve shut-off provides a clear signal that the liquid has reached the shut-off level.
  • Simple and Inexpensive Installation – in both two-point and coaxial fill applications, no additional excavation, manholes or vent piping are required.


  • Simple, Easy and Quick Installation – No excavation or special manholes required.
  • Economical – Costs a fraction of expensive, complicated and difficult-to-install valves.
  • Furnished Complete – 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.
  • No Epoxy Sealants Required!

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All pictures shown are for illustration purpose only. Actual product may vary. All specifications are subject to change without notice.

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