Water Leaks in Condensate Drains
- A central air conditioner has no water within its closed system, just a chemical refrigerant. When the refrigerant is pressurized, it gets cold and the cooling process starts. Within the evaporator, the refrigerant passes through the coil, a series of weaving copper pipes. Warm air from the home is blown over the coil and the moisture becomes attached to the cold copper surface. As the condensation gathers it drips to a catch pan and is drained away from the unit via PVC pipes. A typical AC unit can produce 5 to 20 gallons of condensate daily.
- Most AC units use PVC drains which run from the lowest end of the catch pan located in the evaporator. The drain removes the condensation to outside the home, usually to a drain located near the compressor just a few inches off the ground. Most systems also have a second drain called the secondary or emergency drain. This PVC pipe also leaves from the drain pan, but slightly higher than the main drain. The pipe terminates over a window or doorway with the intention of catching the homeowner's attention. Water from a secondary drain indicates a drainage problem, usually a blockage, in the main drain.
- More often than not, condensation leaks do not come from the drainpipes but from within the evaporator, the component that houses the coil and the condensation drain pan. The evaporator is not intended to hold water beyond the limits of its drain pan. A clog in the main and secondary drain will result in leakage from the unit. Often the evaporator is on top of the furnace and homeowners will mistakenly assume their furnace is leaking. Algae is the most common item to clog condensation drains. The pipes are moist, warm and have a very low pressure flow of water, creating a perfect breeding ground for the algae which will grow until the pipe is completely constricted.
- Clogged condensation drains can be cleaned by a homeowner with a wet dry vac attached to the outside drain. To increase suction, have a helper add water with a little bleach to the drainpipe vent, which is located near the evaporator, while the vacuum is on. If suction won't clean the pipe, then try a plumber's pipe snake. Once the pipe is cleaned, run a cup of bleach down the pipes each month to prevent algae from establishing within the pipes.
- With many newer homes having the AC units in the attic, the PVC drainpipes are subjected to heat in the summer and cold in winter. This can cause the PVC glue to separate and pipes to disconnect. In addition, PVC drains in the attic run along the floor and can be inadvertently crushed by stored items. Unfortunately, some water leaks are not leaks in the pipes, but the result of shoddy construction. Be sure to check your attic-based AC system for secondary drainpipes that empty to the floor. Since this pipe is rarely, if ever used, it can be years after construction before water finds its way out of this pipe and on to the attic floor, eventually dripping out of your ceiling.
