When I first read curiousgeorge’s post, I really wanted to give an answer to his problem. But, honestly, I can’t provide one that suited what I also wish to happen.
In my mind, I want to come out with a conclusion that curiousgeorge have a right over the water tank and pump. In the first place, curiousgeorge will not buy the property if they knew that the water supply is not included in the sale. Or, at least, if they knew that they will be buying a property without water supply, they can at least negotiate a reduction of the agreed price by an amount sufficient to put up water tank and pump to supply water for the property.
Thus, considering that state of mind, I believe the removal of the water tank and pump might be argued as one that will result to a substantial injury on the property bought by curiousgeorge.
For me, if there is unfairness, there should be a law that balances it. Thus, I tried treating the issue as property law problem. In determining the issue: whether curiousgeorge have a right over the water tank and pump, I theorized that it entails the application of provisions of accretion on immovables.
Builder builds on a land of another in good faith might be the applicable law. The previous owner is the owner of materials/builder and Curiousgeorge who should be considered as a land owner; both of them, I presumed, to be in good faith. Thus, curiousgeorge “…becomes the owner of the materials but he must pay for their value. The only exception is when they can be removed without destruction to the work made. In such a case, the owner of the materials can remove them.” (CIVIL CODE OF THE PHILIPPINES, vol 2, 1989 edition, by Edgardo L Paras, page 182) Here is a possible answer, curiousgeorge can demand that the water tank and pump should not be removed because of substantial damage on his part, but he has to pay for their value.
However, curiousgeorge said the water tank was built on a common area. Hence, assumptions must further be laid first. If the title to the entire property has been subdivided into several titles and the original owners retain ownership of the common area on which the tank was build on, the above rule will not apply because curiousgeorge is not a landowner of the lot on which the water tank was built.
So, if the original owners retain ownership of the common area, they also own the water tank and pump (whether these properties be classified as movable or immovable). On the part of curiousgeorge, he only enjoys the use of that common area subject to the easement of right of way (if one is annotated on his title) and enjoys only the use of the subject water tank and pump merely as a usufructury. Thus, curiousgeorge has no right to claim ownership over the subject properties, since the original owner of the land never disposed of them and appears to retain ownership as a Naked owner.
However, if the title to the common area was not retained by the original owners or no subdivision yet made, principle of co-ownership might apply. Curiousgeorge can now object as a co-owner pro-indiviso of the property. Here is a foundation where curiousgeorge can claim ownership over the subject properties.
In sum, even if curiousgeorge was allowed to benefit from the use of the subject properties, it maybe considered part of the previous lease contract between curiousgeorge and the previous owner. When the lease ceased and curiousgeorge bought the property, their sale contract did not cover these properties; hence, previous owner retains them.
It is true that water is a basic necessity. But, I believe that the original owner cannot be considered as a developer of a subdivision, who must provide for these kind of necessity.
By the way, @curiousgeorge, are we talking about water supply from a deep well source?