Tecnología para la protección del medio ambiente - Medición. Regulación. Control.
Piston-type anti-siphon valve KAV
Preventing oil damage

In the case of a leak in the suction line of oil heating facilities which have a maximum oil level in the tank that is above the lowest point of the suction line to the burner, the entire contents of the tank may escape though this leak. The installation of an anti-siphon valve rules out this effect. Even though there is no statistical information on the number of oil heating facilities equipped with an anti-siphon valve, experts claim that there are numerous systems that are operated without any such safety valve. In the case of damage, all costs incurred will have to be borne by the operator.


The new AFRISO KAV piston-type anti-siphon valve is used in oil-carrying pipes of oil heating facilities in which a pipe section is below the maximum tank level. KAV prevents the oil from escaping from the tank in case of a leak in the suction line.

KAV is a vacuum-controlled shut-off system with a completely new function principle: KAV is closed when the burner pump is not in operation. When the burner pump starts, a vacuum is generated in the suction pipe. This opens the KAV and fuel is pumped from the tank. If the suction pipe has a leak or if the burner pump stops, KAV closes and the suction pipe between the tank and the burner pump is shut off. KAV features a pressure relief mechanism, i.e. if the fuel oil contained in the suction pipe heats up and therefore expands, KAV opens. The fuel oil can flow back into the tank provided that a tank withdrawal fitting without backflow preventer is installed. The pressure relief is independent of the adjusted safe height and operates reliably at a response pressure as low as 300 mbar. KAV can be adjusted to any safe height between 1 and 4 m. The adjusted value corresponds to the actual safe height and not to the installation height (as in the case of diaphragm-type anti-siphon valves). This results in reduced line resistance which has a positive effect on the service life of the burner and the pump. KAV is designed as a closed system. The device is vented via the oil-carrying pipe back into the tank. Therefore, no additional vent is required and water or dirt cannot get into the system. Since the diaphragm as the main actuating element has been replaced by a piston, malfunctions caused by pollution, ice or system overpressure are practically impossible.

KAV features 2 G3/8 female connections. It is designed for ambient temperatures from -25 °C to 60 °C and is suitable for outdoor use (in manholes). KAV has a connection for a pressure gauge to indicate the opening pressure or for a pressure relief system or for a test device. KAV is suitable for fuel oil and biodiesel, is odour-tight (PROOFED BARRIER certificate) and has the Technical Approval Z-65.50-415 of the German Institute for Building Technology.

Piston-type anti-siphon valve KAV with pressure gauge
The new AFRISO KAV piston-type anti-siphon
valve prevents oil from escaping via leaks in
the suction line. KAV is also suitable for
outdoor use (in manholes). The system is
odour-tight, suitable for fuel oil and
biodiesel and has the Technical Approval
Z-65.50-415 of the German Institute for
Building Technology.
(Photograph: KAV with pressure gauge)
Kolben-Antiheberventil KAV