If you're about to buy some property that relies on water from a well, make it a priority to get that well checked out. Sometimes old wells are still usable, but other times you may need to drill a new well or find alternative sources of water. Inspecting the well isn't just a matter of looking at it and then testing a faucet; get a good well-services company to check into the history of the well and the condition of the ground around it.
Permits and Maintenance
Any well that you're planning to use should have up-to-date permits (if required by the state), and the maintenance on the well should be current, too. Not only should the pump be in good working order, but the land should be stable, and all pipes should not have leaks and should not show signs of wear or fast patching (for example, if one sprung a leak and was hurriedly patched, that patch could break open the next time the pipe freezes in cold weather).
One problem that occurs with wells in areas where lots of people are tapping the water source or where one well is really sucking up all the water is subsidence. This is where the ground over the water source begins to sink because there's less water holding it up. This has been a major issue in California's Central Valley (particularly the southern San Joaquin Valley portion). While most of the land looks normal, structures like roads, bridges, and even dams can be damaged as the ground supporting them falls at uneven rates. That could mean that if the land around the well is subsiding, the pipes leading to any structures on the property—and the structures themselves—could sustain damage.
Old wells may be drawing from a water source that's dwindling, which would require extending the pump. A well-maintenance company can test the well and see if you're going to face new pump-installation costs soon.
Once you have all of this information, discuss with the well company whether the existing well is still good enough to use or if it will require maintenance or replacement. If the water source that the well is tapping is failing, you need to know that before you buy the land. Lacking a water supply is not good if you plan to build on the land and can't bring city water services out to the area. Contact well companies near you as soon as possible so you can get the information you need before agreeing to buy.
Read more online and on the sites of water-well services companies.