Air & Vacuum Vents

Air gets into an irrigation line three ways: it is there when you fill an empty pipe, it rushes back in when the pump stops, and it collects in pockets at high points while the system runs. Each does its own damage. Fill air slams floats and splits fittings on pump start, vacuum on shutdown collapses thinwall pipe and tubing, and running air quietly adds head loss and cuts flow at the far end of a block.

The vents on this page from Bermad, Netafim, Rivulis and Irritec handle those jobs in three types: kinetic, automatic and combination. The notes below get you to the right type and size for a lateral, submain or main.

Which type of air valve does this line need?

Start with what the air is doing, not with the pipe size.

Kinetic valves and vacuum breakers have a large orifice. They dump the air ahead of the water on fill and let air back in on shutdown so the pipe cannot collapse under vacuum. They do nothing once the line is under pressure. Bermad's K10 covers 3/4" to 2", the 1/2" ARV is the right scale for the end of a lateral or a single riser, and Rivulis vacuum breakers run 3/4" to 3".

Automatic (continuous) valves have a small orifice and bleed the air that keeps gathering at high points while the system is running under pressure. Bermad's A10 and the Rivulis continuous valves open from 1.5 psi, so they work on low-pressure drip zones; the Bermad A30 adds a service port for a pressure gauge. If flow at the far end of a block is below what the design says, this is usually the missing piece.

Combination valves put both actions in one body. They belong on submains and mains, downstream of an isolating valve and on fertigation check valves, anywhere a line fills, drains and then runs for hours. Netafim's Combination vents, Bermad's C-series and the Rivulis 2" combination all do this. Netafim's Dynamic is a diaphragm design that sits normally closed, so a vent at ground level in a dusty yard cannot draw debris into the pipe.

Where do the vents go, and what pressure and size do you check?

Rivulis publishes clear placement rules that hold for any brand: automatic valves on long constant-sloping segments, at peaks relative to the hydraulic gradient, at line ends, before water meters and on filters; vacuum breakers every 150 to 250 m on long continuous lines; combination valves on submains, downstream of isolating valves and on fertigation check valves. A high point is any place the pipe rises and falls again, including a riser to a bench, not just a hilltop.

Check two pressures. The rated pressure must exceed anything the line sees, including pump start. Rivulis vents are rated to 145 psi, the standard Bermad and Netafim vents to 150 psi, some Bermad valves to 175 psi, the Bermad C35 to 230 psi and Netafim's Combination vents to 250 psi. Then compare the vent's opening or closing pressure with the zone's running pressure. The Bermad A10 and Rivulis automatic valves open from 1.5 psi, the Rivulis combination from 2.9 psi, Netafim's Guardian closes at 5 psi on 3/4" and 1", 8 psi on 3" and 10 psi on 2", and the Netafim Combination stays open until 12 psi. A drip zone that runs below the vent's closing pressure will weep all cycle.

On size, a big submain needs air capacity more than thread size. Straight-flow bodies such as the Bermad C15 and C35 pass more air than a standard combination valve of the same size. A downward outlet keeps the discharge off the equipment underneath.

What goes wrong, and how do the four lines differ?

The failures repeat. A block with only vacuum breakers runs short of flow at the far end because nothing bleeds the running air. A 2" combination valve without surge protection lets the water column slam the float shut on pump start and splits pipe; Bermad's C30 has surge protection standard on the 2" and the C10 offers it as an option. A float vent at ground level in a dusty yard can draw debris into the line unless it is a normally closed design like Netafim's Dynamic. A vent sized to the thread rather than the air load makes a big submain slow to fill. A 145 or 150 psi valve on a pump discharge that spikes higher is waiting to fail.

Bermad treats the air valve as a modular control product: K10 kinetic, A10 and A30 automatic, C10 through C70 combination, with coded options for surge protection, assisted closing, a service port that takes a gauge and a choice of outlet direction, mostly in glass-reinforced nylon bodies, with the ARV in acetal. Netafim offers distinct designs rather than options: the high-capacity Combination, the Guardian with sizes to 3" and a published closing pressure per size, the normally closed diaphragm Dynamic and the Pro Air Vent. Rivulis keeps it to three plain types with placement rules spelled out. Irritec vents control air intake and release on Irritec lines, and the Irritec fittings range makes a mixed-brand block easier to join. Send us the block plan and ask about vent sizing.