My house is 100% cast iron radiators. I recently had the upstairs seperated into a second zone. The upstairs zone has 3 radiators all on one loop. The water has to run through one radiator to get to the next one. I'm a little worried that the last radiator may be cold by the time the water gets to it. I just turned the heat on and havn't had much experience with the new set up. So far the last rad is plenty hot, but it is still mild out. My downstairs zone is the original set up. I have two supply lines and two return lines running down each side of the house. Each radiator has a T off the supply and then the water goes into the return line back to the boiler. The water only goes through one radiator before it returns to the boiler. I eventually want to replace the piping on the downstairs zone because it is large. How should I run the zone? Should I have it setup the way it is now? Or would a single loop like what I have for my upstairs zone be ok? The single loop makes me nervouse because of my mother's house. She has single loops for each zone for her baseboard heat and it's much cooler at the far end of the loop. I see a lot of talk about monoflo tees here. My system is all black pipe now and I know I can't go that route if I use black pipe. Is there an advantage to black pipe over copper aside from an installation stand point?

Hi All, I have a Taco ZVC-406 with 3 zones. Zone 1 and 2 are heat and zone 6 (priority zone) is hot water. When I raised the heat, zone 1 should have lit up on the zone control but didn't. I checked the connections and jumped out the TT on both heat zones but no lights. When I switched off the Priority switch, zone 1 lit up and opened the zone. Switched it back to priority and the zone lights went off. :confused: I have had the priority switch on for years with no problems. Anyone know why this might happen? I prefer to use the priority zone for hot water. Thanks