The answer to 'why is my bathtub no hot water' is that the most common causes are a malfunctioning water heater, a broken thermostat, or a problem with the hot water supply line. This can result in the bathtub only getting cold or lukewarm water instead of the expected hot water.
Some common symptoms include the water never getting hot enough, the water temperature fluctuating, or the hot water running out quickly. Potential solutions include checking the water heater settings, replacing a faulty thermostat, or inspecting the hot water pipes for any blockages or leaks. If the issue persists, it's best to call a professional plumber to diagnose and repair the problem.