I just built my own house, and had a high eff. furnace put in. The furnace seems to take forever to kick on after turning up the stat. There is a water trickling sound coming from the exhaust pvc pipe to the outside out the house, and and making a loud banging noise i can hear from my bedroom. There is a step-up in the pvc route before it gets to the outside wall. Is water trapped in the pipe, and can that cause the furnace to stall for long periods before kicking on? If anyone had any advice i would gretaly appreciate it. Also is that water supposed to make it outside or back down to the furnace to drain?