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