Why isn my shower or tub water hot enough when the faucet in the same bathroom provides plenty of hot water?
This is a problem that typically arises during the colder (winter) months when the incoming cold-water temperature starts to drop due to the colder ground temperatures. In most cases the hot water to the house being affected is supplied by a tankless (on demand) hot water system. Tankless (on demand) hot water heating systems are capable of producing a fixed amount of hot water per minute based on certain incoming cold-water temperatures. To provide a comfortable shower or tub/shower temperature during the colder winter months a larger amount of hot water is needed to compensate for the lower cold-water temperature being mixed in the valve. Also depending on the area, a tankless water heater must raise the cold-water temperature from 40°F to 120°F in the winter months, whereas in the warmer (summer) months the cold-water temperature might be 65°F. This increase in demand for hot water typically outstrips the ability of the water heater to produce enough hot water resulting in a luke-wa
