Customer was reporting that the still had temperature differences on hot supply after new recirculating check valve was installed. There are Moen single handle shower valves in both bathrooms that have not been rebuilt since installation. Replaced both valve cartridges and set to temperature originally verified before replacement. Turned on recirc pump and retested temperature. Both readings are the same, 125f in hallway bathroom and 120f in master bath shower. Customer will evaluate over the weekend and let us know if we need to do any other investigation for crossover on hot supply lines.