Hot water to the sink, but not to the shower, same bathroom!
(Oakland, CA USA)
We have a bathroom about 70 feet away from my Takagi tankless heater.
When we turn on the shower, we run it for over 5 minutes, the heater does not turn on, and thus no hot water. This is a new situation, for many years hot water has been delivered, although it takes a few minutes to heat up.
so I ran this experiment.
If I turn on the hot water in the sink, in the same bathroom, the heater turns on immediately, and in 2 minutes I have hot water in the sink.
Then I turn off the sink, and the heater turns off.
I then turn the shower on again. Hot water is there, but the heater is not turning on! The hot/warm water lasts about 5 minutes.
Keeping the shower running, I then turn on the sink. The heater starts immediately, warm to hot water arrives in the sink in 20 seconds. After 2 minutes I turn off the sink, but keep the shower on. The heater keeps going. Hot water in shower continues, for over 8 minutes.
what is the problem? Why does the sink start up the heater, but the shower doesn't???