Can Foundation Movement Damage the Under Slab Plumbing ?

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Absolutely. One of the most common situations found in the foundation business is the damage done to under slab drain pipes when clay soils move slab foundations. Once plumbing pipes break they will start leaking water under the foundation which will compound an existing problem. The leaking water will cause the surrounding clay soils to dramatically magnify in volume, thereby putting uplifting pressure on the concrete slab.

The southern and southwestern portions of the United States have soils with a high percentage of clay soils. Clay soils are different from other soils because they can move up and down, and diagonally and laterally. This movement is caused by expansions and contractions in the volume of the clay soils, which is caused by changing moisture levels. This soil movement is a powerful force of nature and it can easily crack and damage poorly built or minimally functional concrete foundations.

Major cities such as Dallas, Houston, Austin, San Antonio, and Oklahoma City have seen large surges in demand for foundation repair and under slab plumbing repair. There are a number of warning signs of foundation issues that may be causing damage to the under slab pluming. Although not frequent, leaking drain pipes can cause the foundation to develop a hump in the area of the leak. This is primarily due to the substantial expansion of the clay soil in the vicinity of the leak. Any water leakage into the flooring of the house is also a serious warning sign. Other common warning signs are exterior cracks in the brick walls, interior cracks in the sheetrock around doors and windows, and cracks in tile floors.

Although a hump in your floor from leaking drain pipes may not be detectible, the area of upheaval could be large enough to cause cracking in the foundation in other areas of the house. The homeowner may begin to see problems with the doors because they are not easily opened and closed. Or interior wall crack may begin to appear around the corners of doors and windows. The homeowner should be aware of these changes in the home.

Another factor that contributes to homeowner problems with under slab plumbing is the aging material of the drain pipes. Homes built more than 40 years ago were probably built with concrete or steel drain pipes and they are at the end of their useful lives around 50 years. The steel pipes will simply corrode until there are multiple leaks. Concrete drain pipes also experience a corrosion and deterioration process. In addition these pipes are invaded by the roots of scrubs and trees and the roots themselves can damage or break these drain pipes over time.

Today the drain pipes in most newly built homes are PVC pipes. PVC is a tough plastic that is able to withstand more bending and other stresses without breaking than other materials. It can also withstand freezing temperatures without any damage. The useful life of PVC pipes is unknown but it is estimated to be over 100 years and perhaps 150 years. It hasn’t been in existence long enough for users to know its full lifespan.

In conclusion, anytime there has been foundation work on a concrete slab the plumbing under the slab should be checked for leaks. If necessary, they should be repaired immediately to keep the house in good repair.