Recently the water heater (installed upstairs) had a leak so I disconnected it and removed it. There is a ball valve shut off on the cold line into the tank - I closed it to be able to open the main house shutoff, thinking I could at least use cold water in the house until I had a new water heater.
However, the hot water pipe continued to discharge water, roughly a gallon per hour. I had to open a hot water faucet downstairs for the night so at least it would drain gracefully. The day after I installed a bypass pipe from the cold to the hot water and opened the shutoff - this obviously stopped the leak and allowed me to use the dishwasher and the washing machine, albeit with reduced performance.
In the process to replace the water heater I inspected the plumbing system and I could not really find out why a small amount of water was going from the cold to the hot side. What could be a reason for this? I hope I was able to explain the problem.