The manifold return and supply connections will mate directly to the supply and return connections on the bottom of the boiler. Anti-seize / thread sealant is recommended on the connections. Be sure to use the supplied gaskets in the return and supply unions. The manifold is designed to mate with a 1½" heating system loop. If the system loop is a different size, use appropriate fittings to adapt. Ensure system water flow moves in the correct direction, as shown in the drawing below