Ariston Hidden System Leak / Expansion Vessel Issue

Furnace frequently loses pressure over days or weeks without visible leaks.

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

Micro-leaks in pipework, Leaking underfloor heating, Failed expansion vessel, Relief valve passing steam

Safety: Repeated topping up introduces oxygen and can damage the system.

Monitor pressure pattern: Note cold and hot pressures and how quickly they drop.
Check expansion vessel: As described earlier, a failed vessel can mimic a leak by venting water through the relief valve.
Inspect relief discharge: Look for signs of water at the relief valve outlet pipe.
Leak detection: A heating specialist may need to perform pressure tests or use leak detection equipment.

Hard 4/5

Expansion Vessel

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