tap change for electric unvented hot water cylinder Drainage and wastage systems and plumbing help, advice and answers

[Simon H]

Hi

I have an electric unvented hot water cylinder in the loft. I want to change the washer in the hot tap on the ground floor. Do I simply turn off the mains and then run the hot tap down? Then after washer change simply turn back on the mains? I'm unsure about pressure and air bubbles etc...