Heater makes loud popping or crackling noises during heating.

Safety first: Turn off power and allow the heater to cool. Close the cold inlet and open a hot tap to relieve pressure before draining.

Steps:

• Drain tank: Connect a hose to the drain valve (if present) and drain water below the element level or fully if descaling the tank.
• Remove element: Take off the element flange and inspect the element for thick scale deposits.
• Descale: Mechanically remove scale or soak the element in a suitable descaling solution. If the element is heavily corroded or deformed, replace the Tesy heating element assembly.
• Flush tank: Rinse the inside of the tank to remove loose scale particles.
• Reassemble and refill: Install a new gasket, refit the flange, refill the tank, and bleed air before restoring power.