There have been a couple of recent posts about pool leaks, I guess as people get ready to start them up again after winter.
And while my current experience is limited to watching a pool build unfold, once upon a time I did some labor type work for a PB in the midwest.
There were a couple of simple tests to help narrow down where to look for trouble. Time consuming, but the price is right. I've not seen the info all in one spot, but if I somehow missed it, my apology and mods please feel free to delete this post. So,...
Back in the day I was instructed that pool leaks came in two varieties: as either structural or plumbing. The ability to tell one from the other is what I hope to accomplish in this post. Of course, first you need to confirm you have a leak, and the bucket test is as good as any I know. OK, so now you know you have a leak.
Turn the equipment off. Fill the pool up to its normal operating level. When the water movement stills, use a pencil to mark the water level on a grout line. After 24 hours with the equipment off use the pencil again to mark the new level. Barring rain or a strange neighbor, this mark will be below the original mark.
Next, carefully fill the pool back up to its original mark. Now, turn on the pump and let it run continuously for 24 hours. Again, mark the level of the water with the pencil.
If the pencil marks with the pump "off" is at the same level as with the pump "on", it means you have a structural leak and should move on to things like dye tests around the light niche (actually anything that penetrates the pool tank/shell), perform an inspection for shell cracks (look closely for grout line problems - missing grout may indicate bond beam cracks), etc.
If the pencil marks with pump "off" and pump "on" are different (higher or lower), it means you have a plumbing leak.
If the water loss is greater when the pump is "on" (the mark is down lower than the pump "off" line), the pressure side is leaking.
However, if the water loss is less when the pump is running (the pencil mark is higher on the grout line than with the pump "off"), it means the suction side is leaking.
OK, that's it, reasonably simple test, cost essentially nothing (time & pump electricity). Hope it helps somebody. And it would be nice if the newer crowd of PBs and techs could confirm/deny if my reasoning is still valid with modern systems. With modern tech, and maybe with a plumbing leak it would be time to call in the electronic leak detection people?