Correcting crossed water lines in a limited access area Arrived to unit for uncommon issue. Upstairs was vacant and water was off but still had hot water to bathroom sink. Unit downstairs was on. Maintenance opened up multiple spot of Sheetrock so we can further diagnose. Unit downstairs also did not have hot water to lav faucet when water heater upstairs was off. This told me there was a cross in the line somewhere. Came to find out that 2 tees off if the main branch were swapped . MyGuy diagnosed and corrected issue by cutting out tees and re connecting to correct lines. Turned water back on to both units and did multiple tests. Unit water lines are now separated and each unit has its own hot water lines. There are no leaks at this time. MyGuy is not responsible for Sheetrock that was removed.