Viessmann Chronic System Water Loss

Boiler frequently loses pressure over days or weeks

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

Small leaks at radiator valves, leaking pressure relief valve, micro-leaks in pipework under floors, faulty expansion vessel causing PRV discharge

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

Visual inspection: Check all radiators, valves, and visible pipework for dampness or staining.
PRV outlet: Inspect the pressure relief valve discharge pipe outside for signs of intermittent dripping.
Mark gauge: Note the pressure after filling and monitor daily to quantify loss.
Technician leak test: A professional can add leak detection dye, pressure-test the system, and check the expansion vessel and PRV for hidden losses.

Medium 3/5

Pressure Relief Valve

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