Added 3/4†sediment filter to house water main as well as did a Navien combi service cleaning on domestic side of the system of both units, we ran descaling solution through the system for about 45 minutes to an hour And purged the system when finished to flush any solution left in the lines/system. , as well as checked the condisate for any corrosion and also checked the filter screens from the flu pipe for any corrosion and cleaned that as well.