36 on a Vaillant geoTHERM: Low brine pressure (warning, < 0.6 bar)
Short answer
On a Vaillant heat pump, 36 means: Low brine pressure (warning, < 0.6 bar). 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: Low brine pressure (warning, < 0.6 bar).
Part involved: Low brine pressure.
When it shows: Warning message (error memory and Menu 1); no shutdown.
Likely causes:
- Pressure drop in the heat source (brine) system due to leakage or air lock.
Is it safe?
| Does the heat pump stop? | No |
|---|---|
| Severity | Warning |
| Engineer needed? | Yes |
The heat pump keeps running.
Resetting itself: n/a - warning only; heat pump (incl. compressor) stays in operation.
Manual reset: not required.
What you can check
- Note the full code and text shown on the display (and the date/time it appeared). The geoTHERM operating manual says: do not attempt to remove the source of the malfunction yourself; only an expert technician can remedy the fault and reset the error code. Warnings (26, 36) and temporary faults can be noted and discussed at the next inspection.
What the engineer will check
- Check heat source system for leaks, top up brine, bleed.
Who to ask for: Vaillant-trained heat pump installer/engineer (MCS-certified installer).
Certification: MCS ground-source installer; F-gas certificate for refrigerant work.
What you might notice
What owners and engineers report
1 owner and engineer report mentions this.
- No heating on the geoTHERM (VWS/VWW ../2, VWS ../3): 1 report
Sources
- Installation instructions geoTHERM VWS 6-10kW 230V (GB 08/2008) ↗ · 0020046310_01 · page geoTHERM VWS 6-10 kW 230 V 0020046310_01 p.71; geoTHERM VWS/VWW 6-17 kW 400 V 0020057444_01 p.69; geoTHERM exclusive operating manual 0020071929_00 p.26 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026