There are four ways that your plumbing will develop a leak under a slab:

1. Corrosion from soil chemicals
2. Abrasion from long term vibration
3. Pressure from human error or shifting ground
4. Construction defect

Slab leaks from corrosion:

Underground pipes make contact with soil on the exterior of the pipe and water on the inside. Water balance and a charged ground could induce electrolysis in metallic pipes, causing corrosion from the inside or outside of the pipe and eventually causing holes in the pipe.

Hot water lines will more likely corrode from the outside in due to the reaction of the heat and the contents of the soil surrounding the pipe.

Cold water lines generally deteriorate from the inside out due to electrolysis being created on the inside of the pipe.

Electric lines running beneath the slab can also energize metallic pipes and induce electrolysis resulting in corroded pipes.

Older homes with copper pipe usually suffer from chronic plumbing failures due to corrosion. Sometimes the situation calls for a complete repiping of the plumbing. Less invasive repairs can be made with an in-place pipe coating depending on the state of the pipes and the construction layout.

Slab leaks from abrasion:

As water travels through plumbing, vibrations, expansion and contracting may cause the pipe to rub against concrete, gravel, rebar, or other pipes depending on the construction. Over time, the constant vibration and abrasion of the pipe will grate the pipe until it springs a leak.

If pipes are insulated and constructed with stabilizing supports, the vibration can be minimized, prolonging the life of the pipes while protecting if from being exposed to excessive wear.

Additionally, bad joints and lack of coupling adhesion can lead to abrasion at the joints, leading to faster and higher volume leaks.

Slab leaks from pressure:

Underground pipes may experience high levels of pressure from earthquakes, or poor construction. Pipes can be crushed or creased under this type of pressure, depending on the area of pressure. Creased pipes may cause a restriction in flow and low pressure. Additionally, a crease, bend or crimp in the pipe will allow uneven wear and the water will eventually create a hole at the problem areas. Crushed pipes can cause massive leaks over time that wash the soil from under the foundation, putting your property at risk of greater damage.

Pipes need to be spaced and insulated properly in order to avoid being crushed or creased. Many times a crushed or creased pipe can be repaired without a full repipe of the home.

Construction Defect:

During construction, faulty workmanship may not only require rework, but also may result in damage to construction work performed by others.