I am not electrician but this is what I have learned from my past experiences.
I used to have sporadic trip and after getting a electrician to check, he found that I have overloaded my circuit. Thus whenever, all my equipments are running and my fridge compressor were to start running it will cause a overload. Apparently, my tank socket shared the same circuit as my kitchen and when all equipments were to run at the same time, it cause an trip due to overload. So in the end, he re-wired my circuit so that my tank will share the load with my room which don't draw that much current compared to my kitchen.
HDB when wiring the house will share several socket to a 13amp circuit thus our socket is never really 13amp. This is because the typical family do not consume so much electricity.
I am not sure whether this could be your problem but I suggest getting an qualified electrician to look into it if you have any doubts.