Knowing Your Options When You Have a Slab Leak

Understanding Slab Leaks

Generally speaking, when it's been determined that a water line has failed under a slab, there are three options. To fully know the best choice it is prudent to review the causes of what we in the trade refer to as "slab leaks."

One major cause is incompatible soil; that is soil that has some ingredient that causes a chemical reaction, when coming into contact with copper, called electrolysis. This can happen a few months, or a few years after the initial installation, or even several years later. In this case and it's one of the most common causes, total replacement of all under slab copper water lines is not only the proper and best choice, but will be dictated by future slab leaks.

Another cause of slab leaks is improper wrapping of exposed piping. That is, piping that could come in contact with other unprotected lines, rebar used for concrete footing reinforcement and even electrical conduits, or heating duct work. A water line, especially a hot line, will move somewhat when in use, or in the case of hot water lines, as the water changes temperature, it will expand and contract. This movement can cause friction, though slight, that will eventually wear through. Another is a kinked line, or one that was "nicked" by a workman, usually from another trade (concrete workmen are prime suspects). The indentation in the pipe will eventually wear through as the force of moving water gradually, sometimes it takes several years, wears it down. Of course to find out what actually caused the leak is difficult to know.

The one way is to jackhammer the slab and visually observe the cause. This is also, usually, the most economical repair, as well. Sometimes, however, the leak is under something that is expensive to replace, such as a bathtub, shower, tile floor, kitchen or bath cabinets, or a post tension slab. In such circumstances it becomes obvious that rerouting the offending section overhead, though more costly than a typical jackhammer and repair application, is considerably less costly than the alternative (demolishing a tub, or expensive tile floor).

In all cases complete elimination of under slab water piping is best, once slab leaks occur. But in cases where it's been several years since installation, there is no chronic occurrence in the neighborhood or nearby area and the first leak is on a cold water line, it might be a reasonable gamble to use the least costly alternative.

When the work is covered by insurance, one should consider the cost of the deductible when making this determination. After two or three slab leaks, it must be pointed out that total replacement might still cost the same as if one had made that decision on the first one. Add up the cost of the deductible and that is the amount of money spent unnecessarily, along with the inconvenience of the partial repairs.

Every situation is slightly different. You might wonder why water piping is installed under slabs in the first place. There are three main reasons. The first is cost. It is cheaper to loop soft copper from service to fixtures, than to run them above grade in an attic or between floors. Less material is used and no drilling, strapping and protection is needed. Second is noise. Overhead water lines can be heard when water is being used. Some people find it annoying. Not much can be done to eliminate the noise factor (short of soundproofing walls and ceilings). Third is water temperature. Water lines run through attics are subject to extreme temperatures, especially heat. A cold water line that runs several feet to an isolated fixture might take several minutes to deliver reasonably cold water. Hot water lines are best insulated to reduce heat loss. Cold water lines are more difficult to maintain temperature levels, as insulation has little effect on a stagnant water line baking in 140 degree heat. Attic fans are helpful. Most people have little difficulty adjusting to the slight noise increase and occasional temperature increases on cold water lines, however and it should not be a determining factor when making a decision concerning which method to employ.