Help - waste setting on filter drained pool

After 8 inches of rain yesterday in only a few hours my pool was about to overflow. I turned the filter to "waste" but since it was late, left the pump off. This morning the pool level had lowered about 8 inches. Is this normal without the pump running? I've turned the filter back to "filter" but left the pump off till we get (another) huge influx of rain later today. Am I worrying over nothing?

You probably had a siphon going. Quite common if the waste discharge from the waste port is lower than the water level. Most likely to occur with AG pools. Don't worry, just switch the valve to FILTER when you're done dumping water.
Al

Thanks! Actually it's an inground pool, but yes the output is lower than the pool level. I'm just waiting for more torrential rain now...