The picture in the 'Code Check' series shows a 2' necessary rise so who knows?

I've seen city inspectors in my area pass water heater venting that goes right out the top to a 90 and then 1/4" per foot rise (barely) for 10 feet or more to a chimney. It seems crazy and its certainly far from ideal but they let it fly. I really club my buyer over the head with the CO detector thing and will write up the installation as barely acceptable, etc.. I feel it's all I can really do since the installers and the city inspectors won't budge.