All air pumps need to be protected against back-flowing water. For this reason the JBL backflow stop has been developed. This “check valve” just needs to be integrated into the air carrying hose. The arrow on the backflow stop indicates the mounting direction. It needs to pointing away from the air pump.
Tip: install the backflow stop as close as possible to the water surface to stop a possible backflow in good time. Note: check valves for air do not work with CO2! These check valves are also unsuitable for air pipes because the air pressure of the air pumps is not high enough to open the CO2 check valves.