When you say "electric box" could you please clarify what you mean.

Is this part of the fixed installation mounted on a wall with circuit breakers in, or is this en electrical enclosure on a machine, or something else?

OK, so these are parts of the fixed wiring installation in the building yes?

I'm taking this as so unless I'm told otherwise, this is a time that it would be good if we could add pictures, or can we these days, there is a button in the toolbarr in the reply window?

Anyway, OP if you have any pictures and can upload them it would be great and would explain loads.

3ph is still only 230V to earth, so not really any more hazardous to persons in the area than 1ph.

The answer is, it depends, whoever did the installation should have done such to be in compliance with EAWR, generally taken to be in compliance with BS 7671, which means that if this is done correctly the electrical equipment can be right next to water pipes etc. as long as it is suitable for the external influences and the spacing is as per BS 7671.

The same applies to "boxes", as long as they are suitable for the external influences they can even be mounted outside.

However, if the building has been re-arranged around the electrical installation since it was done, then the equipment may not be suitable.

This all depends on the exact scenario.  However, you don't generally expect water pipes to leak.

As an example it would be considered acceptable within the requirements of BS 7671 to have a socket within a kitchen cabinet beneath the sink.

The details are what defines what is acceptable.