Vaillant Reduced DHW Flow / Hydraulic Restriction.

Water heater's hot water output is lower than expected (reduced flow rate).

Advertisements

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.
Advertisements

Repair Difficulty

Easy 2/5

Required Part

DHW Plate Heat Exchanger.
Check Price on Amazon

We may earn a commission from links on this page.

Advertisements