Home inspections investigate drainpipe issues in a somewhat roundabout manner. A lot of drainpipe is not visible and inspectors are careful not to do any testing that is considered invasive. Their concern is more on how the plumbing system functions than with individual components; however, should they detect a leak or find heavy accumulation of moisture, they might analyze the piping more carefully to try to divine the cause. Moreover, much drainpipe is buried outside and hence beyond the inspection\’s scope.

The term drainpipe broadly encompasses a wide range of applications and purposes, both inside the house and outside. This makes the terminology misleading. Inside, drainpipe is that which empties plumbing fixtures and with the aid of gravity funnels waste down to a single point of exit where elevation is lowest. As tributaries join the main line, the diameter grows. (To some, the term drain piping means that it doesn\’t transport solids, whereas waste piping means that it does.) Occasionally vent piping, the purpose of which is to equalize air pressure in the drainage system, doubles up as drainpipe for fixtures on higher floors (a frowned-upon practice).

Outside, drainpipe is used to connect effluent house plumbing with the septic system or sewer. It is also what is used to carry storm water runoff from downspouts to a collection point or daylight away from the foundation. French drains use it to dry out oversaturated regions. Though the various professions dealing with these functions overlap with each other, drainpipe terminology is used in all of them.

Investigating drainage issues in homes may involve inspecting leaks, traps, vents, or floor drains. The cause of a clogged drainpipe might be the wrong type of trap, insufficient slope, double trapping, or a malfunctioning vent. Odors suggest that the water seal of a trap has been siphoned off (either from being an S-type or from excess pressure) or that it has evaporated, which happens in floor drains that are rarely used. There are many potential sources of leaks, including damaged or cracked drainpipe and corroded drainpipe fittings.

Investigating issues outside typically begins with an assessment of wet areas, particularly near the foundation. Gutters and downspouts are checked to see if they connect to a closed drainpipe system that removes storm water from foundation proximity. (Without proper drainage, soil saturates and hydrostatic pressure mounts; if severe enough, foundation walls can crack, tilt, or bow.) The closed drainpipe system should terminate in a rain garden, a retention pit, or daylight. Outside conditions should be compared with crawl space findings to get a more complete picture of how storm water is being managed.

Investigation may extend to additional items such as French drains and sump pumps. French drains are constructed by digging sloped ditches, filling them with gravel, and lining them with perforated drainpipe. High water tables, underground springs, leaks, and lack of a foundation drainpipe system can all cause standing water in the crawl space. This should be drained away naturally by gravity if possible, but when the house is in a bowl the only option is a sump pump.

John W. Gordon is a licensed home and pest inspector working in northwest Washington State. He regularly writes articles and posts blogs about many inspection-related topics, such as drain pipe and plumbing. Visit John’s homepage: www.HomeInspectionWA.net.

John W. Gordon is a licensed home and pest inspector working in northwest Washington State. He regularly writes articles and posts blogs about many inspection-related topics, such as drain pipe and plumbing. Visit John’s homepage: http://www.HomeInspectionWA.net.

Author Bio: John W. Gordon is a licensed home and pest inspector working in northwest Washington State. He regularly writes articles and posts blogs about many inspection-related topics, such as drain pipe and plumbing. Visit John’s homepage: www.HomeInspectionWA.net.

Category: Advice
Keywords: drainpipe, drain pipe, storm water, home inspector, traps, drainage, French drain, floor drain