We recommend the use of at least one (preferably two) Check Valve in the airline to safeguard against water siphoning back into the equipment. Ideal for Aqua Medic Evo Dosers

High quality neoprene valve provides the ideal "Cracking" pressure to reduce surging and also provides a long life.
CO2 and Ozone safe.
Durable construction with easy to read directional arrow for correct orientation at installation.
Clear construction allows visible signs of contamination.

Instructions:
Place the Check Valve in the 4mm ID line from the air pump or CO2 solenoid valve with the Arrow pointing toward the aquarium outlet (away from the equipment).