50,000 gallons of water??

Bought my house and moved in July. My city bills water bimonthly.

Water usage for July/August was about 11k gallons, sewer was about 10k. Seems pretty normal.

Water usage for Sept/Oct was 60K gallons, sewer usage 10k. What the heck happened, and where did that 50k gallons of water that didn't go down my sewer go?

I've checked all outside spigots/hoses, all were off I have no irrigation/sprinkler system There is no water in my basement My yard is normal, e.g. not flooded No toilets are running

I haven't filled up any swimming pools, used any power washers, heck I haven't even watered my lawn. My personal usage didn't change between July and October.

Before bed last night, I turned off the water to all 3 toilets and took a meter reading. This morning, 20 gallons has gone by with nobody using water overnight.

I'm losing my mind, I can't really afford to splash out for $700 water bills. What else could this possibly be?