Poway homes tend to sit on bigger lots, with the tankless out in the garage or on a side wall where it's easy to forget. It does its job day after day, and nobody gives it a second thought until a code shows up or the showers start running cool.
Scale is one common reason. Poway's water is hard, and the minerals settle in the heat exchanger over the years until the unit can't heat the way it used to. Sometimes it's an ignition part or a sensor wearing out instead.
Someone comes out, checks which it is, and gives you a straight answer. If a descale and a part will do it, that's what you'll hear. If it's time for a new unit, it gets sized to your household. You make the decision.
