Bosch
Excessive Pressure / Thermal Expansion
Bosch water heater leaks from the pressure relief valve discharge pipe
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Faulty temperature and pressure relief (T&P) valve, No expansion tank on closed plumbing system, Overheating due to control failure, High incoming water pressure
How to Fix / Troubleshooting
Safety first: The T&P valve is a critical safety device. Do not cap or plug the discharge pipe. Turn OFF power and gas if the valve is discharging continuously.
- Check water temperature: If water is excessively hot or steaming, shut down the heater and call a professional immediately.
- Test T&P valve: Lift the test lever briefly to flush debris, then release. If the valve continues to drip or run, it may be faulty and should be replaced.
- Check system pressure: Have a plumber measure static water pressure. If above 80 psi, a pressure-reducing valve and expansion tank may be required.
- Expansion tank: On closed systems (with check valves or PRVs), install or service a thermal expansion tank to absorb pressure increases.
- Control check: If overheating is suspected, a technician should test thermostats, sensors, and control board.
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Repair Difficulty
Hard
4/5
Required Part
Temperature and Pressure Relief Valve
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