Oso Temperature and Pressure Relief Valve Discharge

Water dripping from the Oso water heater’s temperature and pressure (T&P) 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

Normal expansion discharge due to lack of expansion vessel, Faulty or scaled T&P valve, Excessive system pressure, Overheating due to thermostat failure

How to Fix / Troubleshooting

Safety first: The T&P valve is a critical safety device. Never cap or block the discharge. If in doubt, contact a qualified unvented cylinder engineer.

  • Determine frequency: Occasional drips during heating may be normal. Continuous flow indicates a problem.
  • Check pressure: If a gauge is fitted, verify cold and hot pressures are within Oso’s specified range.
  • Test valve operation: Gently lift the T&P valve test lever to flush debris, then release. If it continues to leak, the valve may need replacement.
  • Inspect expansion vessel: On unvented systems, check the expansion vessel pre‑charge and replace if the diaphragm has failed.
  • Replace T&P valve: Isolate water, relieve pressure, drain to below the valve, then remove and replace with the correct Oso‑specified valve using approved sealing methods.
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Repair Difficulty

Professional Required 5/5

Required Part

Oso temperature and pressure relief valve
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