An installer is asked to replace two aging cast-iron boilers with two mod/con boilers, but reuse as much of the existing distribution system as possible. The system’s owner is also complaining about “sloshing” sounds coming from some of the zone circulators. Since the distribution system is several years old the installer decides to include a Y-strainer to capture dirt particles before they can enter the compact heat exchangers on the new boilers. The system that gets installed is shown in Figure 1 (above). Can you spot several details, omissions or other quirks that will lead to problems over the life of this system?