Water heaters are generally very safe and predictable, especially when properly maintained. Your water heating unit has plenty of monitoring sensors and alarms that help prevent things like carbon monoxide leaks and fires. Generally, your water heater can blow up when the T&P (temperature and pressure relief) valve is damaged, blocked, or plugged. When your water heater is running, the T&P relief valve allows your water heater to release steam, managing rising temperatures, and relieving pressure. If the valve stops functioning properly, pressure can build up in the tank, causing it to explode.