4mm Airline Check Valve – Non-Return Valve (Packs of 2 or 5)

4mm Airline Check Valve – Cheap Insurance for Your Air Pump Here's a scenario nobody thinks about until it happens: the power cuts out overnight, the air pump stops, and with nothing pushing air down the line, water quietly siphons back up the airline and into the pump. Best case, a puddle. Worst case, a dead pump. A check valve stops it. It's a one-way valve that lets air flow down to the stone but blocks water from ever coming back. When You Need One Your air pump sits level with or below the water line You run air into reservoirs, DWC buckets, semi-hydro or ponds You'd rather not find out the hard way How to Fit Cut the airline between the pump and the air stone. Push the valve into the gap with its arrow pointing towards the air stone, away from the pump. Fit one valve in each airline. If no air reaches the stone after fitting, the valve is in backwards. Simply flip it round. 🌿 Rose's Pro-Tip: fit the valve close to the pump rather than near the water. It keeps the valve dry and lets it seal properly. Fits all standard 4mm airline, pumps and air stones. Black Flag Horticulture Ltd, Coventry.