In case anyone else every reads this thread, I found an answer.

I was slowly feeding water into the pool through a pipe embedded in the
concrete deck. At low flow rates, the water clings to the edge of the deck
and a large portion was flowing under the top tile through a small gap in
the grout. The water then migrated several feet to the side and found a
crack in the bond beam at the level of the second tile. I knew there was a
hollow "ring" at this point when tapped and removed the tile. Only later,
when I saw water flow into the crack did I realise it was coming from the
feed line.



--
Remove -NOSPAM- to contact me.