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the new neighbor could complain, and or you could have difficulty selling the property in the future if you don't handle the situation.
You should be able to file an action to quiet title which will give you and all others after rights to have the pump use where it is.
Here are some grounds for your case
Adverse possession, the use since the time the property was subdivided may be included in the calculation of time needed. If you are going to do this you need to quiet title before the owner gives permission which can later be revoke.Easement
by Prior Use If the pump house was on the property prior to and after the subdivision then you can keep the pump house where it is at. This may be a sure winner based on your description.
Easement by prescription similar to adverse possession rights are based on long term use without explicit permission.
When you file to quiet title you would include all of the above as reasons. You only need one to succeed.
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