Was the water main leak determined because they couldn't find any other source? I had a plumber tell me I had a break in my sewer main because he couldn't get his rod to take a bend in a pipe and thought it was a broken. Hired someone else who got through the bend and clean out the pipe all the way to the main sewer. Highly recommend getting a 2nd or 3rd opinion.
Sometimes leaks are not obvious. I recently replaced the flush valve in 2 toilets. Both flappers were slightly warped which I couldn't see until I removed the parts and of course tenants who don't pay water don't care that the toilet tank constantly fills itself. Before dismantling the toilet, put some food dye in the tank wait a few minutes for the color to disperse and then visually inspect the bowl to see if any of the dye is coming thru into the bowl without flushing the toilet, if you see the color in the bowl, time to change the flapper or entire flush assembly.
Also, check all the interior and exterior faucets/spigots.
