From the first sign of water loss due to structural cracking, the immediate action is to stop the crack and make repairs. For a pool repair contractor, the easy buck is to slather it up with some type of bubblegum and call it a day. The water loss stops, they get paid and by the time it starts to leak again in 6 months, they’re nowhere to be found.
Understand this: Epoxy injection is a temporary band-aid, not a permanent repair.
Epoxy injection does not fully penetrate cracks and leaves the damage open on the back side to continue its wrath. If it did fully penetrate the crack, it would still fail as concrete continued to shift. The crack was caused by forces that still exist, either ground movement, pressure behind a pool wall, settling or something that is forcing the two pieces of concrete apart. You aren’t resisting that pressure with epoxy injection. The epoxy is subject to drying, cracking and losing adhesion to the crack as those forces continue to widen and lengthen it. Now you simply have a bigger crack that leaks, with epoxy and other gathered junk inside of it.
Some contractors go the cheap route of pounding rebar into the pool shell, stating that this will keep crack from separating. We have decades of proof that it does not.