My wife and I are looking to buy our first home and have found some promising prospects. One of the homes we like is in what use to be a rural area. Since this house was in a rural area when it was built, it uses a well and septic instead of the city's water system. Upon further investigation, we learned that 6 other homes share the same well and they all contribute to the maintenance of it. Our concern with the well is its depth. We would hate to buy a home that in may run out of water. How does one determine the correct size and depth of the well needed?
The correct depth of a well probably involves several factors such as soil permeability, the level of the water table, and annual rainfall in the area.
I'd think the easiest way to determine if the well will supply enough water is to ask the neighbors who are already using it. They should be willing to share the information with a potential new neighbor/well-sharer.
I'm sure there are more water-usage questions to ask - these were just a few off the top of my head.
There really is NO correct depth for a well. All that matters is if the well is deep enough to draw sufficient water for your needs. In fact, if the well is too deep, you can have problems. For example, there may be a layer of salt if you go too deep.
This can be resolved by questioning the neighbors - is the water supply sufficient?
I'd suggest that as important a question is if the water is good to use. Have that well water tested before you buy. It can be expensive to clean up water if that becomes necessary.
The well needs to be far enough down to reach the underground water table. There may be certain requirements put forth by your local area (township, county, state), but other than that, there's not usually a "correct" depth.
As Doresoom said, your best bet will be to ask the neighbors. They'll know whether there's enough water. Keep in mind, though, that with well water, there is always going to be a chance that you'll run out (if it doesn't typically, a particularly long drought might make you run out).
That said, it's not uncommon for people to build a second (or even third) well, if they have more than one deposit of water under their land. So I wouldn't discount the house just because of the well. Also, since the house is now within city limits, you also probably have the option to hook into the city's water supply (but this might not be the case for all of the houses you've looked at, so the other information may still be useful).
Also, there are a number of ways to help conserve water, or use different water sources. If you're the type that likes to water their lawn, or wash their own car, or keep a garden, you would probably benefit from installing rain barrels to catch the water run-off from the buildings on your property (if you use the water for anything that you will eat or drink, such as a food garden, make sure you have it tested regularly, and/or run it through your filter system). You just have to get creative. :)