Our water bill spiked by 15,000 gallons from last month and I isolated
it to the autofill for our 22,000 gallon pool. When I shut off the
supply to the autofill, the outside meter shows zero flow, but when I
turn it back on, the little "trickle" needle starts spinning. I
watched it for a few minutes and it looks like it takes about 3
minutes for a gallon to flow through, which is pretty consistent with
the spike over a 30-day period.

By the way, we live the Dallas area, so it has been consistently hot,
but not hot enough for that kind of evaporation as we've never seen
this kind of spike before.

Okay, so I'm pretty confident that the pool autofill is where the
water is going. What I can't figure out is whether it is a broken
autofill or a leak somewhere. Judging by the water bill graph, this
started sometime in the last month or so. Where would those 15,000
gallons go and wouldn't I see signs of it in the way of sinkholes? If
it is autofilling and autodraining (we have one of those, too), I
would think that 480 gallons a day would be pretty evident in the lawn
where the overflow drain goes.

Any ideas on how to isolate it? I've left a few messages for pool
repair, but I probably won't talk to anyone until Monday.

Thanks.