Description A check valve (non-return valve) prevents water from siphoning / back-flowing down aquarium tubing when pressure is turned off. For example, when the air pump or CO2 system is switched off. Without this device water will siphon down the tubing an enter your electrical equipment. Instructions Cut your CO2 tubing in the position you would like check valve. Direction of flow can be determined by looking at the valve, you'll see the red plastic is moulded to one end of the unit - that is the input. The other non-moulded end is the output. Push CO2 tubing onto corresponding inlet/outlet as far as you can. Tip: Softening the tubing in freshly boiled water will make it easier to push the tubing onto the valve. Click here to read the full check valve setup guide
