VRC700-MAINT-4 on a Vaillant aroTHERM plus: The water pressure is too low in the heating installation
Short answer
On a Vaillant heat pump, VRC700-MAINT-4 means: The water pressure is too low in the heating installation. The heat pump keeps running. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: The water pressure is too low in the heating installation.
Part involved: System control maintenance reminder.
Likely causes:
- The water pressure is too low in the heating installation.
Is it safe?
| Does the heat pump stop? | No |
|---|---|
| Severity | Warning |
| Engineer needed? | Yes |
The heat pump keeps running.
Resetting itself: cleared by the engineer after maintenance.
Manual reset: engineer resets.
What you can check
- Note the full code and text shown on the display (and the date/time it appeared). Read the heating system pressure on the display (Menu > Live Monitor > building circuit pressure) or the pressure gauge: it should be about 1.0-1.5 bar when cold. Vaillant's operating instructions say to inform your competent person so that they can top up the heating water. Check the filling loop valves are closed and look for visible water leaks or a dripping pressure-relief pipe.
What the engineer will check
- Refer to the heat generator instructions for filling; find cause of pressure loss.
Who to ask for: Vaillant-trained heat pump installer/engineer (MCS-certified installer).
Certification: MCS installer certification; Vaillant product training recommended.
What you might notice
What owners and engineers report
3 owner and engineer reports mention this.
- Pressure keeps dropping on the aroTHERM plus (VWL ../6 A): 3 reports
Sources
- VRC 700 installation instructions ↗ · 0020262579_01 · page VRC 700 installation instructions 0020262579_01 p.36 (Appendix E) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026