The longer the vent, the less effective it will be. It should run directly through the roof to avoid heat loss downdrafts with the possibility of carbon monoxide in the house.: we recently had natural gas run to our home.i was told by our plumber that the vent : had to be pitched.i was wondering what the pitch would have to be.the hot water heater is closer to the front of the house but i would perfer to vent to the back of the house