H07

Worcester Low Water Content / Pressure Warning

Boiler shows H07, often associated with low system pressure or water content, heating may not start.

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.

Possible Causes

System pressure below threshold, air in system, faulty Worcester pressure sensor, leak in heating circuit

How to Fix / Troubleshooting

Safety first: Let the system cool before topping up pressure.

Homeowner checks:

Check the pressure gauge; if low, top up via the filling loop to 1.2–1.5 bar when cold.
Bleed radiators and then re-check pressure.
Look for visible leaks around radiators, valves, and boiler connections.

Engineer checks:

Test the Worcester pressure sensor and replace if it misreads actual pressure.
Check expansion vessel pre-charge and recharge or replace if necessary.
Locate and repair any leaks in the system.

Do not repeatedly top up without addressing the underlying cause of pressure loss.

Repair Difficulty

Medium 3/5

Required Part

Water Pressure Sensor

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