Changing bath mixer tap on Unvented System?

[Hopeflow]

Good Evening all, hope everyone is well.

Im not long out of my time so go gentle please lol.

I have the job of replacing bath mixer tap (no isolation valves fitted under bath). It has an unvented cylinder installed. Is it just a case of isolating mains water, opening taps to drain water out of pipework (inc kitchen tap). Or is there more to it? Ive heard horror stories of them imploding and dont want it happening to me.

 

[ShaunCorbs]

Turn mains off open a few taps let it drain out

 

[Hopeflow]

Turn mains off open a few taps let it drain out

Thanks Shaun. Some people have mentioned opening pressure relief valve, but i thought that was for full drain down of cylinder

 

[ShaunCorbs]

I wouldn’t touch them as they will cause you problems in the end

 

[Hopeflow]

I wouldn’t touch them as they will cause you problems in the end

Ok thanks, appreciate the help.
Just for my knowledge what does cause them to implode?

 

[ShaunCorbs]

When it’s trying to suck the water out eg under vacuum

 

[Hopeflow]

When it’s trying to suck the water out eg under vacuum

Ah ok. Thats what has been confusing me lol. As if mains is turned off and ive got hot taps open, will it not have that effect?

 

[ShaunCorbs]

No just open more than one eg kitchen sink and bath taps etc

 

[Hopeflow]

No just open more than one eg kitchen sink and bath taps etc

Ah ok, thats what i was planning on doing. Thanks again for the advice.