There are many REOs and forclosures in my area. The banks (especially CitiBank) hire idiots to do the winterization.
I explain to my clients that I will come back, for free with 3 days notice, to re-inspect. I also explain that I want the water turned back on my a state licensed and insured plumber, hired by the seller.
I also advise my clients that they should consult their lawyer and get a special contingency agreement, added to the contract, that the closing is contingent on the re-inspection not showing any leaks or water damage.
When there are leaks, the plumber (on site and hired by the seller) has to deal with the damage and the repairs.
NEVER take on any liability that you cannot control!
hope this helps;