If my pool fills up more than halfway above the weir door, the water level recedes back to the middle of the weir door with in12 hours. Is this a leak or normal? It is a kidney shaped, in-ground pool.
Does your pool loose more water another 12 hours later without adding more?
You may have a crack in the skimmer housing or some place else that when the water reaches it, it drains out. An inch a week with no auto-fill is like you said, normal. As long as the water doesn’t drain rapidly past the halfway mark on the weir door, I wouldn’t drive yourself nuts trying to find it.
Respectfully, I would hunt it down. While a leak acting like an overflow preventer sounds like it's doing you a favor, it depends on where it's leaking to. Depending on the soil and other considerations, water getting behind the shell of an IG pool can cause all kinds of issues. If it's not actually an overflow system, you need to find and fix the leak...
Having said that, it wouldn’t hurt to check the easy places first.
Oh I hear you and agree, hence my....
in my response.