We had several days of single-degree temperatures here in Connecticut this past week, and a squatter broke into the basement of an 8-unit apartment building that we manage.  The squatter(s) found a point of obscured vulnerability under a deck (an old boarded-up basement window) and exploited it. It probably happened on Dec 23rd as we started getting no-water calls late in the afternoon of Christmas eve, and it quickly turned into a report of a pipe burst, which ultimately became three burst pipes. The fire dept turned off the water at the street by the time our guy got there, and the City quickly got involved exerting a fair amount of pressure.

In the interests of keeping this story short, these are all the things that we had to do: Communicate with the property owner, the tenants, and the city constantly, offer hotel rooms to affected tenants (some took us up on this), secure the building from future squatters, get the water main and all pipes thawed out, have the water company turn the water on at the street, have a crew of plumbers isolate and repair/replace broken pipes in a muddy crawl space, clean up the mess created by the water in the basement/crawl space, get into all apartments to inspect for damage, test and get water service restored, and repair some internal damage to one of the apartments (that's still in progress), and apologize to the tenants. 

Normally dealing with a problem like this is a big challenge, but dealing with it over Christmas eve & Christmas day with extreme freezing temps when no one wants to work adds significantly to the complexity. Besides the costs, the worst part was that the tenants didn't have water for 2.5 days, including Christmas eve and Christmas day.