When you turn on the hot water faucet, you expect hot water. In fact, you don’t really expect it, you just take it as a given. But if you wait for the water to heat up, and it only gets to “lukewarm,” then you may have a problem with your water heater.
Before we take a closer look at the water heater’s potential troubles, make sure the problem isn’t restricted to only one fixture. If only one fixture is experiencing the issue, the trouble is probably with the mixing valve of that fixture, and you can direct your plumber right to the source of the problem.