OPW 61fSTOP “The Stopper” Overfill Prevention Valves

The OPW 61ƒSTOP Overfill Prevention Valve (“The Stopper”) is designed to prevent overfilling of aboveground storage tanks by providing a positive shut-off during a pressurized-fill (pump-on fill) delivery.

Features & BenefitsOrdering SpecificationReplacement PartsDownloads

Features & Benefits

  • A special crossbar tank-inlet adaptor – is provided with each Stopper to provide for tight-fills and help prohibit open-fills. Mounting hardware, upper drop tube and 14″ lower drop tube provided (longer-length drop tubes can be purchased or added).
  • Completely Automatic Operation – No pre-checks to perform, no resets, and no overrides to be broken or abused.
  • Direct or Remote-Fill Compatible – Fuel delivery couplers can be connected directly to the 61ƒSTOP, or steel pipe can be threaded into the top of the valve and piped to a remote location where the couplers are contained in a 211-RMOT Spill Container.
  • Integral Anti-Siphon Valve – Drain vents on the 61ƒSTOP act as an anti-siphon, by introducing air/vapor into the fill line after the valve actuates, to help isolate the tank from a potential siphon due to a broken or leaking remote-fill pipe.
  • 150 psi (10 bar) Pressure Rated* with Low Pressure Drop – To enable quick, safe delivery of fuel into the tank.
  • 25 GPM (95 L/min) Minimum Flow Rate Required.
  • UL and ULC Listed – To satisfy Third Party accreditation requirements of many jurisdictions.
  • CARB Approved VR-401-A; VR-401-B

*OPW does not recommend pumping pressures above 100 psi for Class 1B fuels or remote applications and we make no warranties for products used in conjunction with the 61ƒSTOP.

NOTE: OPW recommends the use of the 61ƒSTOP with clean product only. Debris and other products such as contaminated waste oil may cause improper operation of the valve.

NOTE: The 61ƒSTOP can be used in gravity drop provided the minimum flow rate is maintained. A tight shut off is not achieved in the closed position. However with a minimum tank size of 1,000 gallons, the leak rate will provide a 30 minute warning before the tank is full.


  • Valve body, adaptor and collar: cast aluminum
  • Poppet: cast aluminum, hard-coated
  • Cam: stainless steel
  • Follower: brass
  • Shaft: CRS zinc-plated
  • Bearing: sintered bronze
  • Float: closed-cell nitrile
  • Nipple: 2″ – 3″ schedule 40 steel pipe
  • Lower nipple: 2″ – 3″ schedule 40 steel pipe with Duragard® coating

Additional Features

“The Stopper” threads into the fill opening and is an integral part of the fill tube. The OPW 61ƒSTOP is fully adjustable to allow for easy installation in new or existing aboveground tanks of various heights and storage capacities.

The Stopper is a single-action, complete shut-off valve. When the liquid level rises to your specific, pre-determined tank capacity, the valve mechanism is released and automatically closes with the flow of the product. Any excess product left between the valve and the fuel delivery coupler is drained into the tank through internal drain vents. The drain vents on the 61fSTOP act as an anti-siphon, by introducing air/vapor into the fill line, to help isolate the tank from a potential siphon due to a broken or leaking fill pipe.

The 61ƒSTOP, available in either 2″ or 3″ full-flow models, maximizes flow rates and minimizes delivery times. The 2″ 61ƒSTOP requires a 4″ tank opening and minimum tank ullage (space from the top of the stored product to the inside top of the tank) of 8″ on the 61ƒSTOP-1000 Cylindrical Float model and a minimum ullage of 4″ on the 61ƒSTOP-2000 Float Arm model. The61ƒSTOP-1000, with the cylindrical float, eliminates the need to position the valve to avoid tank walls or cross-bracing. The 61ƒSTOP-2000 with the float arm allows for increased usable storage capacity in the tank, and is well-suited for small capacity rectangular ASTs. The 3″ 61ƒSTOP requires a 6″ tank opening and incorporates a cylindrical float requiring 8″ of tank ullage space. The 3″ Stopper is a high-flow unit that can accommodate flow rates over 400 gallons per minute (depending on pump capacity).

The 61ƒSTOP-100M and -200M are anodized and compatible with 100% methanol or ethanol fuels. The OPW 61ƒSTOP-305A meets with the specifications of the Handbook of Aviation Fuels Properties for Aviation/Jet Fuel Compatibility (as developed by the Coordinating Research Council of the Society of Automotive Engineers). The 61ƒSTOP-305A is compatible with aviation fuels (including jet fuels), gasoline, gasoline–alcohol fuels, diesel, kerosene, mogas, fuel oil, motor oils (up to 60W) and anti-freeze.

Listings and Certifications


Ordering Specifications and Dimensions

Product No. Description A B C D E F
in. cm in. cm in. cm in. cm in. cm in. cm
61ƒSTOP-1000 2″ Cyl. Float 3 7.6 10 25.4 2 5.1 9 22.4 3-15/16 10 n/a n/a
61ƒSTOP-2000 2″ Float Arm 3 7.6 10 25.4 1/2 3.8 5-18 22.4 1-31/32 5 6 15.2
61ƒSTOP-3050 3″ Cyl. Float 3 7.6 10-5/8 27 2 5.1 8 20.3 5-1/8 13 n/a n/a

Flow Rate for the 61fSTOP 2″ and 61fSTOP 3″

Ordering Specifications and Dimensions – CARB Approved AST Overfill Prevention Valve

Product No. Description in. cm in. cm in. cm in. cm in. cm
61ƒSTOP-1000T 2″ NPT with cylindrical float 10 25.4 2 5.1 9 22.4 9 22.4 n/a n/a
61ƒSTOP-2000T 2″ NPT with float arm 10 25.4 1/2 3.8 5-18 22.4 5-18 22.4 6 15.2
61ƒSTOP-3050T 3″ NPT with cylindrical float 10-5/8 27 2 27 8 20.3 8 20.3 n/a n/a

OPW 61FT Drop Tube

The OPW 61FT Drop Tube is designed to install on the bottom of the 61ƒSTOP AST Overfill Prevention Valves when a lightweight, longer, lower drop tube is required. Constructed of extruded aluminum, the OPW 61FT is connected to the bottom of the 61ƒSTOP by a clevis and cotter pin assembly, and allows for submerged filling of ASTs.

Product # Description
61FT-0206 2″ x 6′ Drop Tube Kit
61FT-0312 3″ x 12′ Drop Tube Kit


Replacement Parts\

Replacement Parts 2″

Product # Description
C04093M 4″ Retaining Collar
C04114RS 14″ Nipple
H12617M Float for 1000 (4 pieces required)
61ARM-2000 Floating Arm Retrofit Kit For 2000

Replacement Parts 3″

Product # Description
D02037M 6″ Retaining Collar
C04474RS 14″ Nipple
C04438M Float (4 pieces required for 3050)