Help! I live in a 80 unit condo (8 floors), with hot water tanks on the top floor (4). They flow down 13 different lines to different units and hot water is recirculated through recirc pipes. Around April several units, around 6, started experiencing boiling hot water that would come out of the cold water faucets (we have levers which you turn for cold/hot). This is happening in the kitchen, bathroom, toilet, bathtub, washing machine, and you have to turn it on for 5-10 minutes and then cold water would finally come out. You have to do this EVERY single time as the boiling hot water would return the minute you turn the fixture off.
The 6 units are scattered through different lines, and throughout the 1st-5th floors of the building with the EXACT same problem, which started at the exact same time. We've had 3 different plumbers come on 4 different occasions. I've had someone even take a look at the drawings and look at the tanks, the pipes, with no answers. No one that we know has made any alterations to their plumbing in their units.
We thought we were getting close when we shut off the hot water valve in unit 102, and the problem was alleviated in that unit and the units above, but no solution was found. All the faucets seemed fine, and cartridges were replaced in shower fixtures that seemed like they were leaking. Turning off the hot/cold water lines to the washing machine in a couple units seemed to help in a couple units, but not for others.
The only work that was done in the building was section was repiped on the ground floor a couple weeks prior to al this (water was shut off, a section of leaking pipe replaced), but the plumber was adamant that did not cause the problem.
One plumber suggested we install individual shut off valves to each unit at a coast of $300 x 80 units (we cannot do it for just the 6), but some say this is pointless as it is expensive and may not even help.
We are at a loss as to what to do. Please help!