All of the skimmer and return lines have been pressure tested. No leaks found at main drain, pool light, or in or around skimmer boxes. There is no equalizing valve.
At this point we're down to 6-7 vertical hairline cracks in the sidewalls at various places. They are so fine you can't get a fingernail to catch. The cracks start about 4" from the normal water height and are 12-20" in length.
If we have covered all usual potential leaks, we're just left to wonder about those cracks, and can imagine that at least in theory, they could be leaking that much.
If others think that amount of leaking from these cracks is possible, what's the best repair process to follow which will not be unsightly?
Thanks for any tips!