The answer to 'water heater no hot water' is that there are several common causes, including a malfunctioning thermostat, sediment buildup, or a broken heating element. Symptoms may include lukewarm or cold water, inconsistent water temperature, or the water heater not turning on at all.
Some potential solutions include checking the thermostat settings, flushing the water heater to remove sediment, or replacing a faulty heating element. However, it's important to know when to call a professional plumber, especially if the issue is with the gas or electrical connections, or if you're not comfortable making repairs yourself.