Manifolds are devices in water systems used to connect the supply and return water of various heating pipes. In underfloor heating and air conditioning systems, brass is preferable for manifold materials, while those for household meter replacement in potable water supply systems are often made of PP or PE. Both supply and return lines are equipped with air vent valves, and many manifolds also have drain valves. A "Y" type filter should be installed at the water supply front end. Each branch pipe of the water supply main should be fitted with a valve to adjust the water volume.