Normal loss here is higher than people expect
Evaporation increases with heat, low humidity, wind, and water temperature. A hot, breezy, dry Central Texas stretch drives all four at once.
It is entirely normal for a pool to lose something on the order of a quarter to a half inch per day in peak summer, and more with a heated pool, an active water feature, or a spa that runs.
Winter loss is much lower — which is why a leak that hid all summer often becomes obvious in December.
The bucket test
Fill a bucket with pool water and set it on a step so it is partly submerged, matching the water temperature.
Mark the water level inside the bucket and outside on the pool wall. Turn off the auto-fill.
Wait 24 hours with normal pump operation, then compare. If both dropped the same amount, that is evaporation. If the pool dropped more, you have a leak.
Run it again with the pump off for 24 hours. Losing more with the pump running points to pressure-side plumbing; losing more with it off points to the shell, the skimmer, or suction side.
Where the water actually goes
Skimmer throats and the joint between the skimmer and the deck are the most common leak point on older pools here, because soil movement works that seam.
Water features and their exposed plumbing are the second, especially after a freeze.
Light niches, return fittings, and the tile line above a settling shell all show up regularly.
Plumbing under the deck is the expensive one, and the one that needs pressure testing and locating rather than guessing.
Why finding it fast matters
A leak washes soil out from under the deck and shell, which is how you get settling and cracking on top of a water bill.
Constant fresh fill water also means constant fresh calcium and constantly diluted stabilizer, so the chemistry never settles either.
An auto-fill hides all of this. If your water bill jumped and the pool always looks full, the auto-fill is doing you no favors.
