How Does an Airlock Form?

An airlock in a pipe forms when flowing water traps a pocket of air, preventing the water from flowing freely.

The Mechanics of Airlock Formation

Here's a breakdown of how airlocks develop in plumbing systems:

Air Entrapment: As water flows through pipes, it can trap pockets of air. This often happens at bends, high points, or changes in pipe diameter.
Obstruction: The trapped air pocket acts as a blockage, disrupting the smooth flow of water. The water can't easily pass through, creating a "locked" situation.
Reduced Flow: The reduced or stopped flow caused by the airlock prevents water from reaching its destination, manifesting as weak water pressure, sputtering faucets, or even a complete absence of water flow.

According to reference information, hot water pipes are more prone to airlocks than cold water pipes. This is primarily because:

Lower Pressure in Cold Water Pipes: Cold water pipes generally operate at lower pressures. This lower pressure environment is less likely to trap air pockets compared to higher-pressure systems.
Higher Pressure in Hot Water Pipes: Hot water systems, due to thermal expansion, often operate at higher pressures. These higher pressures tend to create conditions more favorable for air pockets to form and persist.
Dissolved Gases: Hotter water can hold less dissolved gas than cold water. When the water warms up it releases those dissolved gasses, potentially contributing to airlock formation.

Here are some examples and solutions to consider:

Example: You might notice an airlock when you turn on a hot water tap and the water sputters or comes out in bursts instead of a steady stream.
Solution: A common way to resolve an airlock is by bleeding the affected line. This involves opening a faucet at the highest point in the system to allow trapped air to escape. Another method is to use an air compressor to force the airlock out.

Factor	Influence on Airlock Formation
Water Flow	Can trap air pockets.
Pipe Shape	Bends and changes can trap air.
Pressure (Hot)	Higher pressure increases risk.
Pressure (Cold)	Lower pressure reduces risk.