distance between two pits should not 3m bcoz there is a
tecnical reason behind it, and the reason is that when
there is some heavy earth fault and if one of the pits is
acting as a returning path for earth fault current then it
might go dry due to heat dissipation by the passing
current, and simultaneously one more heavy fault happens
then these pits will offer high resistance because they
have lost moisture and which is not desirable, hence the
distance between two 3m pits should be minimum 6mts.
It can be kept as far away from each other as possible but minimum distance may vary depending upon the length of the earth electrode used. Usually it must be at least the double of the earth electrode's length.
The minimum distance of two earth Pit is two pit no of Earth electrode(Rod , Pipe , Plate).For example
1st earth Pit electrode - 3m
2nd earth Pit electrode - 3m
our two earth pit distance- 3+3=6m
According to your electrodes and requirements
according to bis 3043 1987 one earthing to another distance minimum 3 mtr techinacl reason is if earthing distance lass than 3 mtr than surface area is overlaping and fault curreent desipate to earth. also depend soil restivity and appplication load