No water comes out of the hot tap, or flow is very weak, while cold water pressure is normal.

Safety: Turn OFF power to the heater. Close the cold supply valve before disconnecting any plumbing.

Steps:

• Check that the hot water isolation valve (if installed) at the heater outlet is fully open.
• Inspect any thermostatic mixing valve connected to the Drazice heater. Remove and clean filters and check for limescale; descale or replace the valve if necessary.
• Disconnect the hot outlet union at the heater and briefly open the cold supply to see if water flows freely through the tank (be prepared to catch water). If flow from the tank is good, the restriction is in the piping or mixing valve.
• If flow from the tank is poor, the dip tube or outlet may be blocked with scale; the tank may need to be drained and the outlet cleaned or replaced.