Quite common with central hot water systems. Most commonly it is because hot and cold water intermix at one or more single handle tub/shower facuets or defective laundry washing machine mixing valves. Troubleshooting can be very iritating to those not experiencing the problem because it often requires entering thier homes to test for bi-pass. You didn't say if one or more other apartments have the same problem. If your hot facuets had not even a trickle when you turned your hot water off,the problem is not caused in your apatrment. To prove crossover between H&C,turning hot supply off to intire building should result in hot facuets trickling water crossing from cold supply to hot side. There is another reason albeit rare that can cause this. If hot and cold lines are laid near oneanother for a long distance,the cold water is heated from heated earth.

Thanks for the message. Sorry I was not clear. When I turned off the hot water into my unit, there was no water coming out of our hot water faucets. Not a triclkle.

So that tells you the culprit is in main supply or another apartment. What was the owner's response? Are they having a plumber check it out? Do any other apartments have the same problem?

Your property management company or if you are self managed, hired manager, should be on top of this and have good plumbing companies available doing constant preventive and emergency maintenance at your property who can quickly find out what is wrong. Because of this problem, some condos have banned single lever faucets. If a plumbing problem traces back to such a banned faucet still in use, the owner of it gets the bill.