Detecting Leaks

There are many things in life that can be ignored, a slab leak is not one of them!

Finding a leak in the Water Line

Slab leaks occur in two places, either the incoming water line, which is under pressure or the sanitary sewer line which is not pressurized. If your slab leak is constant and spreading it is probably a pressurized water system leak, an unusually high water bill is also a sign of a pressurized water line leak, which can be seen at the water meter if the center circle or triangular section is spinning or turning. Leaks may become apparent if moisture becomes evident, however some leaks are absorbed by the the ground or spread under the house throughout the sand fill layer and therefore never seen. The water system in your house starts where the main water line comes in, generally next to the water heater, where copper pipes split off the main line and run in the slab to each branch of the house and then split off to each fixture / toilet, sink, tub, etc.at which point the copper pipes go into the walls to each fixture. All of this copper pipe can develop pinholes. Often the culprit is electrolysis caused by copper pipe touching the rebar in the slab. The electrical current created causes a pinhole in the copper pipe.
( see Corrosion and Magnesium Anodes for more information on this subject) To find your water line leak look for water or moisture in the house or use sounding equipment to narrow the search. When the leak is located…

Pinpoint the leak :

Cut the two walls where the copper piping runs through and locate the pipe coming out of the slab,
Cut the section of copper pipe and cap one end, attach an air gauge to the other end,
Fill the section of pipe with air,
If the air gauge moves downward, and air pressure drops, you have found your leak.

The best method to repair a slab leak from a water line is to reroute the entire section of copper pipe. This is done by placing another section of copper pipe into the walls where the original section ran and capping off the line from the slab. The new pipe is then run overhead from the fixture into the attic and brought down to the main line, completely bypassing the old section of pipe. Traditionally with slab leaks the first thought is to break up the concrete and repair the copper pipe, but with this new method there are several benefits:

The slab is not compromised by breaking it apart,
No concrete dust is spread throughout the house while breaking up the slab,
The floor finish is not ruined,
No possibility of repeated problems with the same section of pipe.

Finding a leak in the Sanitary System :

A sanitary line slab leak is due to a broken or cracked pipe or a system that was not installed properly. The system to test for a sanitary line leak is a flood test.

A test ball, an inflatable rubber plug, is put into the exit line of the house,
A toilet is removed,
The sanitary system is filled with water until it is about 1 inch below the floor level where the toilet was removed,
If the water level drops there is a leak in the system, if the water level remains constant, the system is sound.

Once determining that the leak is in the sanitary system, the leak can often be found by placing a camera into the system and viewing it with a monitor. An alternative is an inflatable ball test in which the ball with a long extension is inserted into each branch of the system, if the water goes down, the leak is in that branch of the system. The methods of repairing a slab leak in the wastewater /sanitary lines are either to break up the slab and replace the pipe, or tunnel under the foundation, make the pipe repair and pump the tunnel made with liquid concrete to stabilize the foundation.