That sounds exactly like what happened to us a few years back. It turned out to be a tiny pinhole leak in a pipe inside the crawlspace that we never would have found on our own. It’s amazing how much water (and money) can just disappear like that. We eventually decided to book professional plumbing services ottawa https://superiorplumbing.ca/ottawa/ to do a full pressure test on our system. They were incredibly thorough. The technician used an acoustic leak detector and found the issue behind a basement partition within an hour. They fixed it on the spot and even helped us with the paperwork for the city to explain the sudden spike in usage. They were very professional and saved us from a potential mold disaster. Definitely better to get them in now before it turns into a real flood!