Vaillant
Reduced DHW Flow / Hydraulic Restriction.
Water heater's hot water output is lower than expected (reduced flow rate).
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Possible Causes
Blocked inlet filter, scaled plate heat exchanger, partially closed isolation valve, blocked tap/shower aerators.
How to Fix / Troubleshooting
Safety: Isolate water supply and relieve pressure before removing filters or pipework.
- Clean inlet filter: Remove and clean the cold water inlet filter on the appliance.
- Check isolation valves: Ensure all service valves on the cold inlet and hot outlet are fully open.
- Clean outlets: Remove and clean aerators on taps and shower heads.
- Descale plate heat exchanger: If restrictions persist, descale or replace the DHW plate heat exchanger.
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Repair Difficulty
Easy
2/5
Required Part
DHW Plate Heat Exchanger.
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