Hydrophilic Chemical Grout
If a leak repair project involves a non-structural defect in a concrete or masonry structure, a hydrophilic chemical grout should be used to seal the leak unless job conditions dictate otherwise.
Gels should be used only in below grade structures where either moisture from the interior (like in a manhole) or from ground water is present to keep the cured gel hydrated. Gels will shrink if water becomes absent, but provide a low-cost alternative to foams.
Foams are appropriate for above grade or below grade installation. They are typically 85% air filled after cure and have excellent elongation, compression and rebound for use in expansion joints, cracks, or any other non-structural defect in concrete structures.
Use the aggressive expansion of hydrophobic chemical grouts if repairing a gushing leak that is impractical to repair with milder expanding hydrophilic resins. In below grade structures, this is a good way to fill voids that may be present outside the structure. Once the leak is reduced to a manageable level, hydrophilic resin should be injected into the defect to back up the hydrophobic material.
Inject hydrophilic gel into gushing leaks neat or with a 1:1 water-to-resin mix ratio to shut down gushing leaks. This is a case where you push in as much material as possible as fast as you can. If a high volume pump is available, less material will be used to stop the leak because it reduces the dilution of the resin in the mass of water source.