OPW 99ASV Anti-Siphon Valve for Above-Ground Fuel Tanks

Order codes and specifications

Order code	Size (NPT)	Head pressure setting	Description
99ASV-2150	40mm (1½”)	3m	Anti-siphon valve 40mm × 3m head
99ASV-2200	50mm (2″)	3m	Anti-siphon valve 50mm × 3m head
99ASV-3150	40mm (1½”)	4.5m	Anti-siphon valve 40mm × 4.5m head
99ASV-3200	50mm (2″)	4.5m	Anti-siphon valve 50mm × 4.5m head

Spares: The OPW 99ASV contains no adjustable, replaceable, or repairable parts — no spare parts are available or required.

Application

The 99ASV is designed for installation on top of above-ground fuel storage tanks. Its primary function is to automatically shut off fuel flow in the event of a line break downstream — preventing product loss, environmental contamination and fire risk at the point of failure.

The built-in pressure relief valve handles thermal expansion in the fuel line, removing the need for a separate relief device in most installations.

Installation guidance

The 99ASV must be installed on top of the above-ground tank. The critical measurement for correct valve selection is the A measurement — the vertical distance from the top of the tank to the lowest point of the fuel supply line. This dimension determines which hydrostatic head pressure setting (3m or 4.5m) is required for your installation.

Treloar recommends combining the 99ASV with an OPW 10BM under-pump shear valve for maximum protection against fuel spillage in the event of pump damage or drive-away incidents.

Features

• Automatic line-break shutoff — prevents uncontrolled fuel flow if supply line is severed or damaged
• Integrated pressure relief valve — manages thermal expansion without additional components
• Available in 40mm and 50mm NPT — smaller sizes available on request
• Two stocked head pressure settings — 3m and 4.5m; other settings available on request
• No moving parts to adjust, replace, or repair — maintenance-free service life
• Complies with AS 1940-1993 (storage and handling of flammable and combustible liquids)

Frequently asked questions

What does an anti-siphon valve do on a fuel tank?

An anti-siphon valve prevents fuel from siphoning out of an above-ground tank if the supply line is broken or damaged. The OPW 99ASV automatically shuts off flow at the tank outlet the moment line pressure drops below the set hydrostatic head — stopping spillage before it becomes a fire or environmental hazard.

How do I select the correct 99ASV head pressure setting?

Measure the vertical distance (the “A measurement”) from the top of the tank to the lowest point of the fuel supply line. If this distance is up to 3m, select a 99ASV-x150 (3m setting). If it is up to 4.5m, select a 99ASV-x200 (4.5m setting). Contact Treloar if your installation falls outside these ranges — other settings are available on request.

What size NPT connections are available?

The 99ASV is stocked in 40mm (1½” NPT) and 50mm (2″ NPT). Smaller sizes are available on request.

Does the 99ASV comply with Australian standards?

Yes. The OPW 99ASV complies with AS 1940-1993, the Australian standard for the storage and handling of flammable and combustible liquids.

Are spare parts available for the 99ASV?

No. The OPW 99ASV contains no adjustable, replaceable, or repairable parts. If the valve requires replacement, a new unit is required.

What is the difference between an anti-siphon valve and a shear valve?

An anti-siphon valve (like the 99ASV) is installed at the top of the tank and shuts off flow if line pressure drops — protecting against siphoning from line breaks. A shear valve (like the OPW 10BM) is installed beneath the pump and shuts off flow if the pump is physically sheared away — for example, in a vehicle drive-away incident. Treloar recommends using both together for full above-ground tank protection.

Request a quote

Lead times and pricing for the OPW 99ASV are available on request. Contact the Treloar team with your order code and quantity.