I just installed a dryer vent using semi-rigid aluminum duct. Approximately 7' from where the semi-rigid duct attaches to the dryer at floor level, the duct touches a black PVC drain at ceiling level. The surface to surface contact is probably less than 2 inches. Can the heat from the semi-rigid duct damage or even melt the PVC drain pipe? I suspect the heat from the dryer has dissipated sufficiently at 7' but I have no experience doing this type of work. Thanks in advance for your responses.