The Laws of Stealing and Robbery (16)
1) It is forbidden to do anything which might damage one’s friend even if the act that he does is in his own property. It follows that one may not leave something which has heat and gas and has the power to damage walls next to a wall which belongs to a neighbor unless he keeps it at least three Tefachim (about twelve inches) away from the wall. (Kitzur Shulchan Aruch 183)
2) In the same way one must be very careful not to pour water next to a wall belonging to someone else and if one has a gutter or pipe which are leaking water, they must be placed at a distance of at least three Tefachim (about twelve inches) from the wall. The same applies to anything similar to these things that one must be very careful not to do things which might damage someone else even if he does it inside his own property. (ibid)