Air Pump Manifolds with 18mm Inlet and 4mm Outlets

Air Pump Manifolds with 18mm Inlet and 4mm Outlets

Distribute one suitable air supply to several individually controlled airline runs

These air pump manifolds take a single 18mm inlet connection and divide the air between multiple 4mm outlets. Each outlet has its own tap, so you can adjust individual branches from one accessible position. Choose from 6, 8, 10, 18 or 24 outlets to suit the number of small airline runs in your installation. The larger 18 and 24 outlet steel versions extend the range for systems with more individual aeration points.

A manifold is useful when you want to run several small air stones from one suitable pump, supply separate holding tanks or organise the aeration in a filter area. It provides connection points and adjustment; it does not increase the output of the air pump. The pump still needs to supply enough air for all the connected devices at their working depth.

Choose your outlet count

Option	Inlet	Outlets
6 Way	18mm	Six 4mm outlets
8 Way	18mm	Eight 4mm outlets
10 Way	18mm	Ten 4mm outlets
18 Way	18mm	Eighteen 4mm outlets
24 Way	18mm	Twenty four 4mm outlets

Count the branches you actually intend to use before ordering. An 18 outlet manifold can organise eighteen separate airline connections; the 24 outlet version provides six additional connections. These figures describe the available outlets, rather than a promise that any pump can operate that number of air stones. A small stone in a shallow tank and a diffuser deeper in a pond can place very different demands on the air supply.

If you are expanding an existing installation, include the new diffusers when assessing pump capacity. Adding more branches to an unchanged pump divides the available air between more destinations. Check the pump performance and the airflow required by your stones before deciding whether a larger manifold alone is sufficient.

Check both ends of the airline

The inlet and outlet sizes serve different purposes. The 18mm inlet receives the main supply from the pump connection, while the 4mm outlets feed the individual branches. Match the connecting hose to each fitting rather than assuming the same tube belongs on both sides. Check the outlet or connector supplied with your particular pump: an 18mm manifold inlet does not make every air pump a direct fit.

For the small branches, use airline that fits a 4mm outlet and also fits the air stone at the other end. Our standard sinking airline and heavy duty sinking airline ranges are worth comparing where you want the line to stay down in the pond, but check the selected bore before ordering. A larger bore version is not a direct fit on these 4mm taps. Braided airline can also be useful where its size matches the fitting, but black braided airline does not sink.

When larger outlets are more appropriate

These manifolds are intended for multiple small airline branches. If your diffuser uses a larger connection, or the installation needs larger bore airline, choose the manifold around that requirement. Adapting every branch down to a small outlet can introduce an unnecessary restriction. Compare the 2 Way Air Manifold with 8mm to 14mm Outlets and 4 Way Air Manifold with 8mm to 14mm Outlets for fewer, larger branches.

For systems using four 8mm lines, the 4 Way Air Manifold with 8mm Outlets offers another connection arrangement. You can compare the options together in our air pump and aeration range. Choose by the actual connections and airflow requirements, rather than by outlet count alone.

Positioning and commissioning

Position the manifold where you can reach every tap and trace each airline. In a system serving several tanks or filter compartments, a simple label on each branch makes later adjustments much easier. Allow space around the inlet connection and avoid pulling the manifold sideways with tightly stretched hose. Keep the air pump installed in accordance with its own instructions, including the required protection against water reaching the pump.

Check each hose connection before starting the system. Once running, inspect every air stone rather than assuming that visible bubbling in one area means all branches are working. Different airline lengths, diffuser depths and stone conditions can produce uneven delivery. Adjust the taps gradually while watching the connected outlets. Do not close every outlet against a running pump; follow the pump instructions for permitted operation and air distribution.

Keeping the system working well

If a branch becomes weak, check for a kink, a loose connection or a clogged stone before changing the settings on every tap. A blocked diffuser can make another branch appear stronger because the air distribution has changed. Work through one branch at a time so you can identify the cause and restore the intended balance. Isolate equipment appropriately before disconnecting or maintaining it.

Our ceramic air stones and ceramic flat air discs provide options for individual aeration points. Check the connection and airflow needs of the selected size. If you are unsure which arrangement suits your pond, tell us the pump model, airline lengths, water depth and number of diffusers, and we can help you choose compatible components.