Ok, so we've had the pool about 18 months, and I've been saying all along that the autofill isn't working properly, and I finally got my husband to listen.
The autofill appears to be set to the appropriate level. However, if I have the valve at the hose bib open, the pool will gradually fill over 3-5 (it moved about a 1/2 inch higher in 36 hours since we marked it). But I can't hear the water running like you do if we raise/lower the float. It seems silent - I just went out and verified that I can hear it when I trigger the float/autofill. If I shut the valve at the hose bib off, the pool does not fill - so the problem is somewhere with the autofill, right?
Is it possible that when the valve is open, that the water leaks slowly and silently into the pool, thereby gradually filling it up? If so, where I do look for the problem and the fix?
Is this making sense??