Low
S.76 on Vaillant ecoTEC Pro 24

Your boiler is warning you that the water pressure is getting too low to operate efficiently, though it may still be working for now.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

What the manual says

Manufacturer manual

Service message: Check water pressure. A service message is activated. Check the water pressure.

Shared across the range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This message is triggered when the internal sensor detects that the system's water pressure has dropped below the ideal operating level. It is usually caused by a small leak in the pipework, air being bled from radiators, or a component like the expansion vessel losing its charge. Because the pressure is low, the boiler is struggling to circulate heat effectively around your home.

This warning is more frequent in autumn and winter when homeowners turn their heating back on after a long break or bleed their radiators to remove cold spots.

DIY fix possible

Locate the filling loop valves underneath the boilerSlowly open both valves until you hear water movingMonitor the pressure gauge until it reaches between 1.0 and 1.5 bar, then close both valves tightly

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