How can you have waste pipes for underground stories of a building?

For example, my waste pipes are buried a few feet under my yard because I only have a crawlspace. If I had a basement, I imagine they would just have to dig the pipes deeper, which would still be possible because the city lines would most likely be deeper than my basement. But, what if you had a really deep basement or a commercial building that went several stories underground?


2 Answers 2


If sewage can no longer flow downhill by gravity, then a grinder pump would be installed at the lowest point to pump the sewage up to the sewer line.


I know of a property in Tyler TX in which the 2 acre lot slopes away from the street so that the sewer under the house (on a slab or pier and beam, no basement) is well below the level of the sanitary sewer main under the street. The drain from the house slopes down to a holding tank near the street where it is pumped up to the sewer main. The pump turns on when the level in the tank reaches a set point.

The owner told me the house was originally on a septic tank which drained downhill from the house and he converted it to this system with an inducement from the city. He asked to install a larger tank than the city code allowed so that in the event of a power failure (common there due to many trees and aerial power lines) he would have more time before the holding tank would get full, but the city would not grant a variance.

A house near me in Dallas TX was remodeled and a bathroom put into a converted garage. This house is on a slab very high above the street and sewer main so the house waste drains by gravity. The contractor told me he installed a mini-tank and pump, for the added bathroom only, to take the waste over to the sewer line at the vertical clean-out 4 ft from the foundation. He said it would have been more costly to slope the line down to the level of the existing house sewer line.

Yikes! I would not do it that way if at all possible in the budget. Eventually the electric pump will fail.

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