Navien offers the new Ready-Link manifold system for NPE tankless water heaters. The kits are available in configurations of two, three and four units side by side and two and four units back to back. They can be installed new or retrofitted. Multiple manifold systems can be combined to support up to 16 cascading units in 30 different arrangements. Each component of the manifold system is portable and fits through a standard door opening, making same-day assembly easy, the company says.