Description
The tube is the run between the pump and the nozzles. It is supplied in long coils so a line can be laid with joints only where a nozzle or a change of direction requires one, which is what keeps the number of potential leak points down on an installation with dozens of nozzles.
Material and pressure rating are the two specifications that decide whether the tube is fit for the system, and they go together. High pressure misting runs on nylon or stainless tube rated for the pump; low pressure misting runs on polyethylene at mains pressure. The two look similar in black and are not interchangeable - polyethylene tube on a high pressure pump will swell and then part at a fitting. Ask for the material by name and the working pressure in bar, not for "misting tube".
Black is specified for outdoor runs because a pigmented wall does not pass light: an unpigmented tube in Gulf sunlight grows algae internally, and algae is what blocks a 0.1 mm nozzle orifice. Whether a given black tube is also rated for long-term UV exposure of the wall itself is a separate question and worth asking, particularly for a run clipped to an exposed pergola or roof.
When ordering, state the outside diameter and wall thickness or bore, the material, the working pressure at the temperature the line will actually reach in summer, the coil length, and the fitting type the tube has to suit - push-fit and compression fittings do not accept the same tube tolerance.