7H-04 on a Daikin Altherma: Water flow problem during domestic hot water production
Short answer
On a Daikin heat pump, 7H-04 means: Water flow problem during domestic hot water production. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Water flow problem during domestic hot water production.
Part involved: water flow / circulation pump / flow sensor.
When it shows: Water flow abnormality determined mainly during domestic hot water.
Likely causes:
- Closed stop valve in the water circuit.; Air in the water circuit.; Water flow is too low.; Water pressure is too low.; No by‑pass installed in the water circuit.; Faulty water flow sensor.; Faulty 3‑way valve.; Faulty water pump.; Faulty hydro PCB.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: no.
Manual reset: Manual reset via user interface.
What you can check
- Read the full error code and sub-code shown on the user interface (Malfunctioning screen; press the help button for Daikin's long description) and note it, with the date/time, for your installer.
- Check the heating-system water pressure reading on the gauge/display: Daikin operation manuals ask users to check it is above 1 bar. If it is below that, report it to your installer (do not open the unit).
- Do NOT bleed radiators while an error/malfunction symbol is displayed: Daikin operation manuals warn refrigerant may have leaked into the water circuit - ventilate and call your installer.
- If heating/hot water has stopped, the operation manual lets the user confirm on the Malfunctioning screen whether the backup/booster heater may take over as emergency heating (much higher running cost) until the installer attends.
What the engineer will check
- Check that all stop valves of the water circuit are open. . ; Purge the water circuit. . ; Check the water flow. . ; Check the water pressure. . ; Check if a by‑pass is installed in the water circuit. . ; Perform an electrical check of the water flow sensor. . ; Perform a check of the 3-way valve. . ; Perform a check of the water pump. . ; Perform a check of the hydro PCB. . ; | Troubleshooting.
Who to ask for: Heat pump installer / heating engineer.
Certification: None specific for water-side checks; MCS-certified installer recommended.
What you might notice
What owners and engineers report
13 owner and engineer reports mention this.
- No heating on the Altherma: 7 reports
- Keeps stopping / cutting out on the Altherma: 2 reports
- No hot water on the Altherma: 2 reports
- Radiators cold on the Altherma: 2 reports
Sources
- Service manual Daikin Altherma 3 M EBLA/EDLA04~08E (ESIE22-09) ↗ · ESIE22-09 · page 20 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026