Vented Loop Anti Syphon Valve - w/ Fixed Vent

For Engines Mounted Near or Below the Waterline
If the point where cooling water is injected into the exhaust hose is less than 6" (15cm) above the waterline, when the engine is shut off there is a risk that cooling water will siphon back into the exhaust system and subsequently into the engine itself.
Such siphoning may be prevented by fitting an air vent in the cooling water (raw water) injection hose at least 16" (40cm) above the waterline (see image).

Four different models of Vetus Anti Syphon Devices are available in two different styles:

The AIRVENT models featured here have a "flat top" shape and a fixed direction vent fitting on the top.
AIRVENT models are available in "V" or "H" versions:

"V" (AIRVENTV) models have a normally-closed, integral anti-siphon joker Valve that allows air to enter the exhaust system to break the siphon when the engine is shut off. These models are completely self-contained, and need no additional equipment.

"H" (AIRVENTH) models have no valve, but come with 12 ft of Hose which is led to a supplied overboard thru-hull fitting. This hose allows air to enter back into the exhaust system to break the siphon when the engine is shut off.
These "hose" models have the advantage of being maintenance-free. (No valve to become clogged with salt crystals, or to spray when clogged.)

All "V" models can potentially become clogged with salt crystals from water drying on the valve when the enine is off, and must be periiodically cleaned. With AIRVENTV models, this requires removal from the bulkhead and dissembly of the unit.
For "V" models, a replacement set of 4 valves is available as a spare part. See Related Products.

Features –
• Acts as a siphon break when the injection point of exhaust cooling water is close to the waterline
• "V" models have a reliable antisiphon pressure valve and are self-contained but require periodic maintenance to prevent clogging with salt crystals.
• "H" models come with an overboard bleed hose and are maintenance-free since they have a connection to the outside of the hull. Cooling water bleeds through this opening while the engine is running. Fortuitously, this can provide a valuable, real-time, visual check of whether your engine water pump is functioning properly. H models come complete with 12 ft of hose, a thru-hull fitting, and hose clamps
• "Cut to Size" — can be fit to a variety of water injection hose diameters: 1/2" (13 mm), 3/4" (19 mm), 1" (25 mm), 1-1/4" (32 mm)
• All models have the same mounting hole pattern and are interchangeable, if necessary
• Plastic housing