The answer to 'why is my drain no hot water' is that there is likely an issue with your water heater or the plumbing connecting it to the drain. Common causes include a malfunctioning water heater, a clogged or damaged pipe, or a problem with the water supply line. Symptoms may include lukewarm or cold water coming from the drain, and the water heater may not be heating properly.
To troubleshoot, first check the water heater itself to ensure it is turned on and functioning correctly. If the water heater seems to be working, the issue may be with the plumbing connecting it to the drain. You can try clearing any clogs or blockages in the pipes, but if the problem persists, it's best to call a professional plumber to diagnose and repair the issue.