Worcester Bosch Chronic Pressure Loss

Boiler frequently loses pressure and needs topping up every few days.

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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

Leaking radiator or pipework, Faulty pressure relief valve passing water, Failed expansion vessel, Internal leak in plate heat exchanger

How to Fix / Troubleshooting

Safety first: Do not over-pressurise the system. Repeated topping up can introduce oxygen and cause corrosion.

  • Visual leak check: Inspect all visible radiators, valves, and pipework for signs of water, staining, or green/white deposits.
  • Check PRV discharge: Look at the pressure relief valve discharge pipe outside. If it drips when the boiler runs, the PRV may be passing.
  • Engineer diagnosis: A technician should test the expansion vessel charge, replace or recharge it if flat, replace a leaking PRV, and pressure-test the system for hidden leaks.
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Repair Difficulty

Medium 3/5

Required Part

Expansion Vessel
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