We are an Uponor/Wirsbo "partner" service/installation company here in Minneapolis. The old unit can be a bother. We replace the zone valves if we must, but would rather convert them to the much more reliable thermal actuators. When replacing a the old Wirsbo zone valves we usually start with the valve, adapter ring and top off with the new actuator. This is especially true if they have leaked in the past. We also check for water quality as this can have a long lasting negative effect on many of the radiant floor heating system components.