Gunite pool leaking....? best ways to stop the leak(s)

[etbrown4]

I have a large 10 yr old gunite pool which has been leaking for some time, however with the moderate earthquake in Va last year, it has been leaking more. About 2-3" overnight. Leaking stops about 6" below the normal water level.
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.

Right now the water level is down 30" for the winter. We'll plan to repair or fill the cracks, refill in a few weeks, and dye test then to be sure what we have.

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? What about Vulkem 116 or silicone.

My pool is considered nominally black in color, but actually it is dark gray. Some think it may be called a 'quartz' finish - not sure.

Thanks for any tips!

[PoolDoc]

If the leaking stops at 6" below the normal water line, the leak(S) are NOT pressure side piping leaks, and are NOT at the main drain or light. They ARE somewhere at or above the minus 6" level, possibly in or around the skimmer or tiles, but also possibly in the cracks. 2" overnight, on a 20x40 pool is ~1000 gallons per day, or about 0.7 gpm. Several small cracks can definitely do that.

I wouldn't use silicone; it tends to get nasty looking and not last very long. But, I don't know what would be best; others may.

[etbrown4]

ok, so if not silicone, what else might we try?

[waste]

Welcome to the Forum!

While the plumbing lines were tested, was a visual inspection of the skimmers done? (I've seen frost-heaved decks crack the skimmer body, I suppose an earthquake could do similar damage)

[etbrown4]

We tested the skimmers in the summer before the minor quake. A pretty close visual lately turned up nothing. As soon as it gets a little warmer, we'll fill the pool and recheck the skimmers. We'll also check the tile line closely around the full perimeter. Thanks for the tip!