When I turn on a faucet I get just above warm water. If I turn a second faucet on at the same time I get scalding hot water. I know it's not the hot water heater, it's new and turned up really high. I used to get hot water from one faucet at a time. My plumber was clueless. How can I get hot water out of one faucet at a time.

You don't have a recirculation line in your system do you?

Do you have a clothes washer?

Are there single handle faucets or two handle units?