High-efficiency furnaces are also known as condensing furnaces. Thus, it is normal for high-efficiency furnaces to create some form of condensation during their operation process. This is because they have two heat exchangers, which create water. As the two heat exchangers absorb so much heat that the exhaust gas changes from a gas state to a liquid state. Thus, creating condensation that is then drained through the condensate line. Note: to maintain a high efficiency rating your furnace must be properly serviced so it can efficiently drain the excess water that condensates. If there is a build-up of condensation or any kind of leak or clog, the condensation can’t be carried out of your home and ends up pooling around your furnace system.