Solution: Assuming that the original planned monthly water consumption is X tons, the current monthly water consumption is X-3.

260/(X-3)-260/X=6

260X-260(X-3)=6X(X-3)

XX-3X- 130=0

(X- 13)(X+ 10)=0

x = 13； X=- 10 (s)

That is, the original planned monthly water consumption is 13 tons.

(2) The actual water consumption for four months is:13 * (1+40%) =18. 2 tons

The annual water fee is 4*[ 18]. 2* 1。 1+2( 18。 2- 12)]+8[ 13* 1。 1+( 13- 12)*2]=4*32。 42+8* 16。 3=260。 08 yuan.