Overfill Prevention Valves

Masterflow Overfill Prevention Valves protect overfilling of the tank, thus avoiding environmental spill. A full range is available to suit underground tanks, above ground tanks for fuel, oils, water and chemical installations. Manufactured from quality components, Masterflow provides the peace of mind necessary for such a simple yet crucial device. 

Preventing overfill is essential for many reasons.  Without it, the impact can be catastrophic and include:

  • Major fines from environmental and regulatory authorities.
  • Loss of liquid or fuel, thereby affecting the efficiency of your operation or production capacity.
  • Damage to the environment.
  • Significant cost to your business.
  • Damage reputation in the market.

However, a correctly sized and good quality Overfill Prevention Valve, as supplied by Masterflow Solutions, will help protect you from the above, and assist in the following:

  • Compliance to AS1940, AS1692 and other important regulatory standards.
  • Fulfilling best industry practice.
  • Meeting your obligations to the refuelling company.

AS1940 contains several clauses about overfill prevention, one of which is “Overfill prevention shall be provided by an alarm sounding and the flow of liquid being stopped, before the tank overflows.” The proven method of overfill prevention is a mechanical valve, and in some applications an Overfill Alarm is also necessary to comply with AS1940 and AS1692.

Overfill Prevention Valves

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Overfill prevention valve Model MF-OPV2 is a economy model 50mm device ideal for small day tanks and the like.

It can be screwed in through the top or bottom of a 50mm BSP socket, which means you don’t need to access the tank internal to fit this valve.

It is designed for gravity flow on above ground tanks only.

Model 446 can be used in both gravity or pumped filling applications up to 850L/min.

It has a two stage positive shut-off and pressure rating of 4-8bar.

In 50mm size, it is available in both Aluminium and Stainless steel construction, but in the 80mm size, only in Aluminium.


Model 445 is an overfill prevention valve designed only for gravity filling up to 350L/min and is available as a 50mm device only.

Overfill prevention valve Model 442 is designed to provide maximum fuel storage capacity within your tank.

It is suitable for both gravity fill, and pump fill up to 1000L/min.

Constructed from aluminium, it is available as a 80mm valve only.

It is also available as a horizontal mounting device – please ask for further details.

Model 440 is also a shortened overfill prevention valve, ideal for gravity filling up to 550L/min on the 50mm (2”) device, 600L/min on the 80mm (3”) device and 800L/min on the 100mm (4”) device.

It is of aluminium construction and suitable for a max pressure of 0.65bar.