Dimplex 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 Dimplex expansion vessel diaphragm, Passing Dimplex pressure relief valve, Hidden leak in pipework or radiators, Micro-leaks on Dimplex boiler connections

How to Fix / Troubleshooting

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

User checks:

  • Inspect for visible leaks: Check all radiators, valves, and visible pipework for damp patches or staining.
  • PRV discharge: Look at the external PRV discharge pipe for signs of water staining or dripping.
  • Record pressure: Note the pressure when cold and when hot. Large swings may indicate expansion vessel issues.

Professional repair:

  • Test and recharge or replace the Dimplex expansion vessel.
  • Replace a passing Dimplex PRV.
  • Pressure-test the system to locate hidden leaks.
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Repair Difficulty

Medium 3/5

Required Part

Dimplex expansion vessel
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