Under Slab Leak Detection

Most customers are unaware that a plumbing leak even exists. Even if you do not have a foundation problem, you should test for plumbing and sewer line leaks. Over time, leaking and broken sewer lines can cause significant home foundation repair problems. Aftermath recommends that if a leak is in question, it’s important to get the plumbing addressed first; even if the plumbing is the only thing addressed. Aftermath has the experience and knowledge to identify leaks from the symptoms showing above the foundation to know if a leak test is needed.
Under slab leaks generally come in two forms, sewer leaks and leaks in water lines. It’s important to distinguish the difference between the two types of plumbing systems.

Water Supply Line Leaks

If your water lines are leaking, you’ll know it! Some signs of a water leak may include:

  • A larger than usual water bill.
  • Water seeping through the slab or out from under the slab into surrounding soil.
  • A warm or cold feeling under the foundation where the leaks have occurred.
  • Unusual wet areas in the landscape around the home.
  • A drop in water pressure inside the house.
  • Cracking in the foundation or in paved areas around the house.

Even a pin hole in a water line can leak out over 8,000 gallons in one month. With a pressured supply water line leak, the introduction of this water into expansive soils can sometimes cause upheaval of the foundation. The expansion of the soil typically represents the area of the leak in question by revealing a dome shaped area of heaving.
If you have noticed a few of these signs happening at your home or business, it is time to call in an expert. Aftermath Structural Repair offers pressure testing for supply line leaks.



Sanitary Leak Testing

Sanitary leaks can cause two reactions as the leaking water begins to react with the soil beneath the structure. The initial leak may cause a slight upheaval when it is introduced to the soils. As the leak progresses with time, the foundation may begin to settle downward in that particular area.

A few other signs of a sanitary leak include:

  • Consistent sewage backups and blockages.
  • A sewer odor.
  • Indentation in the lawn or the pavers around the lawn.
  • Foundation cracks.
  • A rodent or insect infestation.

Sanitary leaks can be detected through the following two types of testing, both of which Aftermath Repair can perform:


Hydro-static Testing

1.) A hydrostatic test begins with locating the sewer cleanout or installing one if required. Prior to the early seventies, cast-iron piping was used for the sanitary drainage system under residences. Many of these older homes had multiple sanitary systems exiting from beneath the foundation in different locations and joining together in the yard before connecting to the city sewer main. Each of these independent sanitary systems must be tested separately, requiring time to locate and possibly excavate each exit from beneath the foundation. Homes constructed after the early 1970’s generally use plastic piping (ABS and PVC) for their sanitary drainage, have only one exit from beneath the foundation, and typically have a readily accessible main cleanout. In general, a four- or five-bathroom home constructed using plastic sanitary piping can be tested more quickly and less expensively than a one-bathroom home constructed using cast-iron sanitary piping. PVC pipes usually fail because of significant foundation movement, mature tree roots growing into pipe joints, original poor construction.


2.) After a cleanout has been located or installed, and a sewer camera has been used to inspect the system, a test-ball is inserted into the piping and inflated near the perimeter of the foundation.


3.) The piping is then filled with water, and the water level is monitored at a first floor shower or commode flange. A falling water level indicates a leak on the system. Additional tests (isolation and flow) are necessary to determine the location of the leak(s) and whether or not the leak(s) allows drainage to escape the piping under normal service conditions.


The cost of a hydrostatic test through an existing cleanout averages between $250 and $400. The variance in the basic hydrostatic test price depends on the following factors: How difficult was it to locate the cleanout? Was in necessary to remove and reset a commode to observe the water level during testing? How extensive was the video pipe inspection? What type of documentation was requested (written report, photographs, drawings, copy of video inspection)? On older homes with multiple independent cast-iron sanitary systems, many of which will require locating and excavating, the hydrostatic testing of all the independent system may easily double or even triple the average price. In general, regarding time requirements, houses constructed since the early 1970’s typically require about two hours for hydrostatic testing. Houses constructed prior to the early 1970’s may take anywhere from two hours to an entire day, depending on the number of independent sanitary systems and the need for excavations, cleanout installations, and removing and resetting commodes.

Isolation leak testing

Once a hydrostatic test has been performed and failed, the next step is to perform an isolation test. It’s important to find out exactly how many leaks exist and under the foundation as well as their location so that an exact repair plan can be made. Essentially, the isolation test is a process of elimination. Inflatable test balls are inserted into the clean out in several locations to block off or isolate each section of the plumbing separately. Once the lines have been blocked off, they are filled with water and then monitored. This process is repeated section by section until the leak is located. After the general area of the leak has been located, a camera
can be pushed down sewer lines for a closer inspection. Once isolation testing is done a map of the house indicating the line locations and leak locations is drawn up and then a repair proposal is written based on the results of the test. Repairs vary from repairing the leaks found to total under slab system replacement.

Find how Aftermath can help you.    Services Contact Us >