I just had my water heater replaced by a plumber. Now the hot water flow and pressure is about 1/4th of what it used to be at the upstairs tub faucet. Other faucets in the same bath seem low as well but it is hard to tell. The bath tub faucet had great flow before and would fill the tub in 5 minutes. The plumber said he did not cause the problem but after talking to him more he said that the old water heater was plumbed backwards (cold water inlet was connected to the hot fitting on the heater and the hot water out let line was connected to the cold fitting on the heater). So I switched the hot and cold flex pipes around so they would be backward like it was before the water heater was replaced. Now I have great flow at the tub faucet but the hot water temp seems to cool off before the tub is full. Any help

Much appreciated.