This Polypipe stainless steel manifold is the largest of the range with twelve ports and is suitable for use with 15mm or 12mm pipe. Please note: If using 12mm pipe (as with the Overlay and Overlay Lite systems) you will need to use PB181512 Adaptor sets. Manifolds are used in all underfloor heating systems above 30m/sq, irrespective of floor type. Manifolds are supplied complete and fixed with a wall mounting bracket. The manifold comes complete with the drain and air vent assembly, which can be positioned on either end of the manifold, and isolation valves are supplied separately for the supply end of the manifold. Each manifold includes a flow meter on each port making it possible to precisely control the flow of water through the system for even and energy efficient heating.