My Furnace Air Separator Is Leaking

Air Separator Purpose

• It is crucial to remove the air that is created in a hydronic system during the water-heating process. The air will corrode connection lines and fittings in the system, eventually causing leaks and reducing the amount of heat produced by the furnace. The furnace air separator, or air scoop, removes this air from the system of connection lines that supplies heat to the radiant system that heats the home. The air separator is located between the boiler and the expansion tank in order to remove the accumulated air before it reaches the circulating pump.

Air Separator Function

• Cold water that enters the boiler contains air molecules, which are released when the water is heated. The furnace air separator is designed to separate the air from the heated water and send it through an outlet line to remove the air from the system. The inlet line at the air separator is larger than the supply line, which naturally causes the water flow to slow down and release the air. A float within the air separator is raised by this escaping air, which rises to the top and is vented through the tapping valve. A leak in an air separator will develop at the inlet and outlet orifices or at the tapping valve on top.

Proper Installation Avoids Leaks

• It is very important to install an air separator correctly to prevent leaks from developing, as well as to avoid noise in water lines and heat distribution components such as radiators and circulation pumps. A furnace air separator has arrows embossed on the outside to indicate the water flow passing through the separator. This is a common area of improper installation, as are the many pressure and check valves that are normally part of the hydronic system.

Common Causes of Leaks

• Air accumulation is just one of the potential causes of leaks in a hydronic system. The flow and temperature of the water passing through the system are also crucial aspects in the system, and any malfunctions in these areas will lead to corrosion from air accumulation as well as pressure and temperature imbalances that create undue force on valve and line fittings. It is important to make sure that pressure relief valves, check valves and aquastats are installed and operating properly to avoid leaks in other areas of the system, including the air separator.