Kockney Koi 4mm Airline Connectors – Packs of 5

Kockney Koi 4mm Airline Connectors – Packs of 5

Choose a straight joiner, 90-degree bend or T-piece for your airline layout

These Kockney Koi connectors join standard 4mm airline in pond and aquarium aeration systems. Each option contains five fittings of the selected shape. Choose straight joiners to connect two lengths of airline, 90-degree bends to turn a line around a corner, or T-pieces to connect three lengths at a branch. They are small, push-on fittings for the airline itself, so check the hose size and layout before choosing your pack.

The three shapes solve different problems. A straight connector keeps an extension in line; an elbow changes direction; a tee introduces a branch. Selecting the appropriate shape helps keep the hose route tidy without pulling a tight bend into soft airline. Five fittings in a pack also give you matching spares for later repairs or changes to the arrangement.

Which connector shape do you need?

• Straight joiner – pack of 5: two ends for joining one length of 4mm airline to another. Choose this when extending an existing run or replacing a damaged section while retaining sound tubing.
• 90-degree bend – pack of 5: two ends arranged at a right angle. Useful where the airline needs to turn beside a filter, around the edge of a tank or inside a compact equipment area.
• T-piece – pack of 5: three ends for joining three lengths of airline. Use this when planning a branch to separate air stones, with sufficient pump capacity for the combined arrangement.

The pack contains five of one shape, rather than a mixed selection. Choose the shape you require from the options. Airline, air stones, an air pump and any separate flow-control or non-return valves are purchased separately.

Match the fitting to 4mm airline

Kockney Koi specifies these connectors for 4mm airline. The hose pushes over the connector ends; this is different from a fitting into which rigid pipe is inserted. Check the internal size of the existing flexible airline, especially when a supplier lists both the internal and external measurements. A hose with a larger bore will not become a secure fit simply by pushing it further onto a smaller connector.

For a weighted hose route in the water, choose the 4mm option of our Standard Sinking Airline or Evolution Aqua Heavy Duty Sinking Airline. Select the matching bore on those pages. If your installation uses 8mm airline, see the separate Kockney Koi 8mm Airline Connectors instead. Keep the bore consistent across the connection unless you deliberately need a suitable reducer.

Planning a branch with a T-piece

A T-piece provides a connection between three hoses, but it does not regulate each branch. Air follows the resistance of the complete route, including hose length, water depth and the diffuser at the end. Two different air stones or different installation depths can therefore receive unequal amounts of air even when they share the same tee.

If you need individual adjustment, include suitable separate airline control valves or use an appropriate manifold. Do not assume that adding another branch increases the pump’s output. Check the pump’s instructions and capacity for the intended depth and all connected diffusers. Keep the route as straightforward as practical and avoid unnecessary lengths or repeated fittings that complicate maintenance.

Fitting and checking the connection

Plan the route before cutting the airline. Leave enough length to reach each connection without pulling on the fitting, but avoid loose loops that can snag during filter maintenance. Follow the air pump’s instructions when switching it off or disconnecting equipment, and maintain any alternative aeration needed by the fish while you work.

Cut the hose end square with a suitable clean cutter. Inspect the tubing for splits, hardened ends or damage, and replace unsound sections. Push the sound hose securely over the connector end. A correctly sized connection should feel snug; do not force a mismatched hose or leave a loose connection in service. Support the surrounding tubing so that the fitting does not carry its weight or remain under sideways tension.

Once the system is reconnected, restart the air supply and check every outlet. Look for normal bubbling at the intended diffusers and listen for air escaping from accessible joints. If one branch performs poorly, inspect the hose route and diffuser as well as the connector. A kink, blocked air stone or unsuitable depth can affect delivery even when the joint itself is secure.

Routine care and useful spares

Check the fittings when cleaning air stones or servicing the air pump. Replace a connector if it is cracked or no longer grips sound, correctly sized tubing. These open connectors are not non-return valves and will not prevent water travelling back along the airline when the pump stops. Follow the pump manufacturer’s siting and backflow-protection guidance for your installation.

Keeping a spare pack with your pond maintenance equipment makes small repairs easier. Store unused fittings somewhere clean, then inspect them before use. For a new layout, count the actual joints and branches first so that you order the correct shape and number of packs.