Trying to find out what the total length is of the expandable vent for AO Smith’s GDV-40 water heaters. AO Smith customer service says they don’t know and to reference my supplier who also doesn’t know. Checked with my hvac supplier who can get the part, and he says there’s no info and when he calls AO Smith they also tell him they don’t know. Literature says that max horizontal venting is 80”, but they don’t provide actual total length. Anyone have any idea?