Leaking into alley

[nixontop]

I have a small in-ground pool. In the past when I forgetfully allowed the water to overfill the pool, the water would run out into the alley about 6 feet from pool perimeter.

4 weeks ago, I vacuumed pool. Ever since, water is running into alley (when pump is on) as if it were over-filling.

q1- how does the overflow system work? (there is no visible overflow drain)
q2- can there be any correlation between over flow system, my vacuuming, and the flow of water into alley? Or does this sound like a leak in return line that is pure coincidence?

Thanks.

[ChuckGeo]

An overflow system allows excess water to leave the pool and maintain a normal water level. There is usuially a square grate at the waterline, althiough I have seen then as a pipe through the sidewall of the skimmer.
You may have a leak in your return line - the line that blows water into the pool. Return line leaks are typically worse when the pump is on. Does you filter have a multiport backwash valve? Does the backwash line run towards the alley? If yes to both questions, you might have a leak through your multiport valve and going out the backwash line. After vacuuming, did you backwash? A bit of debris might have gotten stuck in the valve, preventing it from closing completely. I'd try backwashing again to see if anything will flush out of the valve.