Air trapped in a water main is the hidden cause of many "mystery" problems: reduced flow, noisy pipes, inaccurate water meters, pressure surges and even burst pipes. Air valves — in Georgia often called *ვანტუზი* or *вантуз* — are a small line item in a project BOQ, but they protect the whole network. This guide explains which air valve to choose, where to put it and how it works together with gate valves and dismantling joints.
Why air gets into a pipeline
Air enters a water network in three ways:
- During filling – the pipe is full of air that must be pushed out.
- During operation – dissolved air comes out of solution at high points and where pressure drops.
- During draining or a pipe burst – a vacuum forms, and without an air inlet the pipe can collapse (a real risk for thin-wall PE and large steel pipes).
Three types of air valve
| Type | What it does | Typical use |
|---|---|---|
| Single-function (air release) | Releases small pockets of air while the line is under pressure | Local high points, after pumps, before meters |
| Double-function (kinetic / large orifice) | Exhausts large volumes of air during filling and admits air during draining | Long mains, start/end of slopes |
| Triple-function (combination) | Combines both: large-orifice in/out plus small-orifice release under pressure | Default choice for most trunk and distribution mains |
For utility networks, the usual specification is combination (triple-function) air valves to EN 1074-4, with ductile-iron bodies (GGG40/GGG50) and a flanged connection, PN10 or PN16.
Where to install air valves
A practical placement checklist for engineers and contractors:
- At every high point of the profile.
- At the start and end of long horizontal runs, and every 500–800 m along them.
- At sharp changes of gradient (from a gentle to a steep downhill slope).
- Downstream of pumps and upstream of large check valves.
- Before bulk water meters and flow meters — air in the line is a leading cause of meter error.
- On both sides of a gate valve that is used to isolate long sections.
Always install an isolating gate valve under the air valve, so the air valve can be serviced without shutting down the main.
How to size an air valve (quick rule)
Air-valve size depends on the main diameter, filling and draining rates, and the slope. As a starting point:
| Main diameter (DN) | Typical air valve size |
|---|---|
| DN 80–200 | DN 50 |
| DN 250–400 | DN 80 |
| DN 450–700 | DN 100 |
| DN 800–1000 | DN 150 – DN 200 |
For long trunk mains and steep pipelines, size the valve with the manufacturer's selection curves and confirm the vacuum protection rate.
What to write in the BOQ
*"Combination (triple-function) air valve to EN 1074-4, DN 80, PN 16, ductile-iron body GGG50 with epoxy coating, flanged EN 1092-1, with anti-surge (non-slam) feature; installed on isolating gate valve DN 80 in drained chamber with lockable cover; positions as per pipeline long-section."* List each valve by its chainage, so the contractor installs it at the high point and not where it is easiest to reach.
Quick selector
- New PE100 village network, DN 110–250 → DN 50 combination air valve + DN 50 gate valve in a meter-style chamber.
- Pump station discharge, DN 300 → DN 80 triple-function valve with anti-surge (non-slam) feature.
- Steel trunk main, DN 800 → DN 150–200 combination valve, isolating gate valve, and a dismantling joint for maintenance.
What GON supplies
GON LLC supplies combination and single-function air valves, ductile-iron gate valves DN 50–1000 (PN 10/16/25, GGG40/GGG50), and dismantling joints DN 50–1000 from stock in Tbilisi. We have supplied armature and PE100 pressure pipes for village water supply projects such as Banoja and Dmanisi.
Related products: Gate valves · Dismantling joints · PE100 pressure pipes · Water meters & flow meters
Further reading: Gate or butterfly valve on distribution mains?
Do PE pipes need air valves?
Yes. PE pipes are lighter and more flexible than steel, but they are still affected by air locks, and a vacuum can deform thin-wall SDR17/SDR21 pipe.
What is the difference between an air valve and a vacuum breaker?
A vacuum breaker only lets air *in*. A combination air valve both lets air *in* and releases it *out*.
Should the air valve sit in a chamber?
Yes. Use a drained chamber or a valve box with a surface cover so the valve can be inspected and protected from frost.
Get a project quote
Send your BOQ, pipeline profile or drawings to sales@gon.ge or call +995 595 818 800. GON delivers across Georgia, including Tbilisi, Batumi and the regions.
GON supplies drainage, water, gas and road-infrastructure products to contractors, utilities and IFI-funded programmes across Georgia.