Chemical grout was first developed and applied in 1955. Since that time it has been used to stop leaks in sewers, manholes, tanks, vaults, tunnels, and many other applications all over the world. Recent studies and over 40 years of experience indicate that America´s first trenchless technology is still the best, most cost-effective, long-term defense against infiltration of groundwater into structurally sound sewer systems.
Chemical grout forms a waterproof collar around leaking pipes and manholes. Chemical grouts do not stop sewer leaks by simply filling joints and cracks. Instead, grouting chemicals are forced into the surrounding soil where they gel with the soil into a waterproof mass which cannot be extruded back into the sewer system.
This water-tight collar adheres to the outer surface of the pipe or manhole where it will stay indefinitely unless removed by excavation or exposed to sunlight for long periods of time. If groundwater pressures increase, the collar will be pressed even more tightly against the structure, increasing its ability to stop leaks.
If the humidity in the soil declines for a long period, the grout may begin to dry, also. However, when the soil humidity returns, the grout will absorb moisture and return to its original condition. The soil humidity around leaking manholes and sewers is almost always high enough to prevent any significant shrinkage of the gel.
Most infiltration enters structurally sound sewer systems through joints, manholes, service connections, and the first few feet of the service lateral. The best, and most economical, way to stop these leaks is with chemical grout. Chemical grouting usually costs less than ten dollars per foot for average residential lines. That makes it the least expensive rehabilitation method available, and it is also the least disruptive.
Roots are often a costly, destructive intruder in sewer pipes. They can enter through microscopic openings, then quickly grow in size and strength. This growth can crack and move even the strongest pipes, leading to leaks which overload treatment plants, clog pipes with silt, and wash away essential side fill support.
Mechanical cutters will clear a pipeline temporarily, but they also stimulate growth. Chemicals can kill the roots and retard new growth, but the residual chemicals are washed away in a year or less. However, when a special growth inhibitor is mixed with chemical grout, it is encapsulated and cannot be lost. As a result, roots cannot penetrate the protective gel.
Air Test Procedure
The testing device shall be positioned within the line in such a manner as to straddle the pipe joint to be tested.
The testing device and elements shall be expanded so as to isolate the joint from the remainder of the line and create a void area between the testing device and the pipe joint. The ends of the testing device shall be expanded against the pipe with sufficient inflation pressure to contain the air within the void without leakage past the expanded ends.
Air shall then be introduced into the void area until a pressure equal to or greater than the required test pressure is observed with the void pressure monitoring equipment. If the required test pressure cannot be developed due to joint leakage, the joint will have failed the test and shall be sealed as specified.
After the void pressure is observed to be equal to or greater than the required test pressure, the air flow shall be stopped. If the void pressure decays by more than 2 psi within 15 seconds due to joint leakage, the joint will have failed the test and shall be sealed as specified.
Joint Sealing Procedure
Joints showing visible leakage or joints that have failed the joint test specified shall be sealed as specified. Joint sealing shall be accomplished by forcing chemical sealing materials into or through faulty joints by a system of pumps, hoses, and sealing packers. Jetting or driving pipes from the surface that could damage or cause undermining of the pipe lines shall not be allowed. Uncovering the pipe by excavation of pavement and soil (which would disrupt traffic, under mine adjacent utilities and structures, and cause further damage to the pipelines being repairs) shall not be allowed.
The packer shall be positioned over the faulty joint by means of a measuring device and the closed circuit television camera in the line. It is important that the procedure used by the contractor for positioning the packer be accurate to avoid over pulling the packer and thus not effectively sealing (grouting) the intended joint. The packer ends shall be expanded using controlled pressure. The expanded ends shall seal against the inside periphery of the pipe to form a void area at the faulty joint, now completely isolated from the remainder of the pipe line. Into this isolated area, sealant materials shall be pumped through the hose system at controlled pressures which are in excess of groundwater pressures. The pumping unit, metering equipment, and the packer device shall be designed so that proportions and quantities of materials can be regulated in accordance with the type and size of the leak being sealed.
Upon completing the sealing of each individual joint, the packer shall be deflated until the void pressure meter reads zero pressure, then reinflated and the joint retested as specified. Should the void pressure meter not read zero, the contractor shall clean his equipment of residual grout material or make the necessary equipment repairs/adjustments to produce accurate void pressure readings. Joints that fail to meet the specified test criteria shall be resealed and retested until the test criteria can be met.
Residual sealing materials that extend into the pipe, reduce the pipe diameter, or restrict the flow shall be removed from the joint. The sealed joints shall be left reasonably flush with the existing pipe surface. If excessive residual sealing materials accumulate in the line the manhole section shall be cleaned to remove the residual materials.