Also, if let's say I install a waterproof case, it is OK to install a RCD there? My unit is all with 15A socket, so can this socket connect to RCD and this RCD connect to heater? I assume it is OK while outside the toilet, there is normal double pole switch.

Should I use normal 1P+N RCD or 2P RCD?

Meaning DB box should be fitted with a RCD?

So is it OK if it is installed above e water outlet?

Ain't it ugly to install such protector there? beside not safe.

Try install ontop far away or outside the bathroom. Get a proper design RCD which look better. I already post some example above.

If have 2P, than get the 2P.

Yes.

It means we are shortchanged? Anyway, replacement is to just replace this ELCB with a RCD right?

The model number is CE240B from Hager. Is this ELCB or RCD? Because I see this word Earth Fault Indicator...

Yup. Ask your developer if it is a new house.

"A residual-current device (RCD), or residual-current circuit breaker (RCCB) is an electrical wiring device that disconnects a circuit whenever it detects that the electric current is not balanced between the energized (line) conductor(s) and the return (neutral) conductor"

Is is a RCD.

Oh. So it is my misunderstanding? SO even a RCD also displays e earth fault indicator?

Only if the pipe not in the wall, and way above or away from water reachable area. Last time we had a maid when she clean the bathroom, she was till the top tiles that mean the ceiling also wet can you imagine such maid wash this bathroom. Sure get electrocuted.