When the main drain line access is below the level of the basement floor and the cover is open, it usually means the drain line is being used to allow basement water to drain out. The following photo shows an attempt by a homeowner to use the sewage pipe to the city sewage system for draining the basement. This method of draining the basement is hazardous. Sewage gas or raw sewage itself could back out of the access opening. Most municipal sewage systems do not allow ground water, roof runoff, or foundation seepage water to be discharged into the sewage system. In this particular case the homeowner installed a check valve on the pipe, a check valve is suppose to allow drainage in only one direction. As it can be seen in the photo the check valve has failed.
During periods of heavy rain the volume of waste water that flows to the sewage treatment plants can exceed the plant’s treatment capacity. This not only increases the sewage treatment costs, but in some cases it forces untreated sewage to be pumped into the ocean, rivers or lakes. This is why some beaches are closed after heavy rainfalls. Ground water that seeps into the basement should only be pumped to an outside yard area or dry well. The drain pipe access cover should be reinstalled. A sump pump installation will likely be needed when the drain pipe is no longer available to drain the basement. In addition to this basement having a serious water infiltration problem, sewage backup could pose a serious health hazard. A good home inspector will check for an issue like this one.
Photo taken by Dennis Robitaille of Able Home Inspection.