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Risk Factors for Slab Leaks

Cracks from a leak

An Invisible Enemy: Risk Factors for Slab Leaks to Look Out For.

A slab leak is a water or sewage leak under or inside of the concrete slab on which a house is built. So many things can cause slab leaks that it’s difficult to say without knowing your home just how likely it is that one may develop there. The purpose of this article is to explain the main reasons why slab leaks happen so that you can identify your risk factors and look for clues. Although there are some symptoms that are easy to identify, a formal diagnosis may be difficult to come by without a plumbing professional who is experienced in handling these anomalies.

Construction Defects

The cause of slab leaks that is most often talked about is a defect in construction. It is true that Orange County has had a spate of slab leaks and that a number of them have their roots in 1950s construction methods that may have fallen short of the ideal. Poor construction is not the only cause, however, and anyone discovering a slab leak under their home should not automatically assume that the people who built it are responsible.


Under certain circumstances, electrolysis can occur in metal pipes carrying water underground where the metal is in contact with electrically charged soil on the outside and water on the inside. In such cases, the pipe corrodes and eventually leaks. Pipes carrying hot water are more likely to corrode from the outside because of the heating of the soil. In the case of cold water pipes, the electrolysis is created on the inside of the pipe and that is where corrosion will usually begin.

If there are electric lines also running beneath the pipe, they can energize metal pipes and initiate electrolysis that induces corrosion. The copper pipe found in older homes often causes total plumbing failure when it corrodes. In such homes, owners must completely replace the plumbing, or else coat the pipes with an anti-corrosion substance.

Long-term vibration

Water traveling through pipes can cause vibration and/or repeated expansion and contraction of the pipe. If it is too close to concrete, gravel, other pipes or rebar, this constant vibration against something solid will abrade the pipe over a period of time until it leaks. This kind of abrasion can also happen if the joints were poorly constructed.


Earth tremors are not exactly unknown in California and can cause high levels of pressure as easily as can construction. A pipe crushed or bent by the pressure of this type will restrict the flow of water, causing water pressure to build up until the pipe bursts. This sort of leak can have catastrophic results, as it can wash the soil from under the home.

Clay soil foundations

Orange County has many areas with clay soil, and clay is a reasonably common cause of slab leaks. The problem with clay is that it expands when it’s wet and shrinks when it’s dry; that sort of movement adds to the risks listed above. If underground plumbing is connected to the slab (and there will almost certainly be places where it does) then as the soil expands and contracts it can loosen the fittings or cause a crack. In either case, a leak follows.

Insurance coverage and its limits

Slab leaks must be caught early. The damage they cause if untended can be extremely expensive to repair. To make matters worse, there is a strong possibility that when a leak has been left untouched for some time, the home insurance covering the residents will not pay to correct the slab leak damage. Though this will vary from case to case and insurer to insurer, generally speaking, the insurance company will pay the cost of leak detection and some drying out costs, but not the cost of repairs. This is particularly true when it is clear that the condition has existed for some time but only recently been found. Unfair though it may seem, the insurance company is likely to view such cases as negligence on the part of the homeowner.

Indicators of slab leaks

You don’t want to break through your concrete and start digging until you’re sure that (a) you have a slab leak and (b) you know where it is. Plumbing companies that specialize in the detection and repair of slab leaks have specialized electronic detection tools to help in the search for the problem. Call an expert plumbing vendor that specializes in slab leaks in the event you notice any of the following warning signs:

  • The sound of running water, however faint, when all water is turned off.
  • A hot spot on the floor (this could indicate a leak in the hot water pipe).
  • Mildew or excessive mold under the carpets.
  • A cracked slab.
  • A water bill far higher than you would expect, or a water meter that runs even when there are no fixtures in use.

If you spot any of these symptoms, don’t panic! The cause may very well be something other than a slab leak. However, if you do indeed have one, you will need the skill of an experienced plumbing team to identify the problem, locate the leak, and provide the least invasive method for reaching and repairing it. Jackhammering through concrete is no small matter; it alters your foundation and affects your entire house. The right professional will provide a number of effective options for reaching your leak and sealing it.



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