Have you recently installed a high-efficiency gas furnace and turned other gas appliances into "orphans"? This well could be the case because when furnaces are replaced, more often than not, they are high-energy-efficiency models that increase comfort and save money on fuel bills. However, they are not vented out through the chimney (as was their predecessors). Rather, newer models with high-energy "star" ratings are vented through the wall with PVC pipe, instead. The result: The remaining gas appliance -- usually the water heater -- is "orphaned" and now vents into the chimney all by itself. The problem is the chimney might be too big for one appliance alone, and dangerous venting and fume issues can arise. If you are installing a high-efficiency furnace, mention this to your HVAC contractor, or if it's already in, have them come back to check your little orphan appliance today. And that's the On The House tip for today.