Well Construction

Many of us might imagine a water well to be simply a hole in the ground, or a six-inch pipe sticking up somewhere in the backyard. But a drinking water well is more complicated than that. To understand how these structures work, it’s important to first know how they’re constructed.

When installing a well, the driller must first drill through something called overburden. This is the layer of topsoil, sand, clay or gravel just above the bedrock. There is often a lot of water in the overburden. Unfortunately, this water is often not pure enough to drink. Drillers must install a steel pipe or casing to keep the contaminated water out of the well. It is best if the casing is installed at least ten feet into competent bedrock.

Most drillers insist on a minimum of 40-feet casing to keep drinking water safe. Since casing comes in 20-foot lengths, it must be connected, either with a weld, or by using threaded pipe. Threaded and coupled pipe is generally thought to be the better way to go, since the homeowner won’t have to deal with a poor or cracked weld later on.

Casing must extend above the final grade level of the property. A good rule of thumb is 18” above grade. This will help keep surface water from entering the well. Also, when installing the first piece of casing, a flame hardened drive shoe will prevent surface water from entering the well, and seal the casing into the bedrock.

Of course in order to be able to install the casing, the driller must drill a larger diameter hole. Since surface water will take the path of least resistance, it can flow down along the casing and possibly enter into the well through micro fractures before it is properly filtered. Grouting – a process of installing an expanding grout into this space to seal it off from surface water infiltration – will solve this problem. This is not a requirement in Pennsylvania, though several municipalities have had the foresight to require it.

In our area, most wells are open borehole construction. This means that once the well is in bedrock, there is an open hole through the bedrock. The well is drilled until an adequate supply of water is obtained from inlets – really nothing more than cracks and fissures in the bedrock through which water flows. If you’ve driven on an interstate, you’ve probably noticed water flowing out of the rock (or ice in the winter). This is how a water inlet works when it flows into a well.

Once the well is drilled, the installer will place a pump, and pipe water to the house. A four-foot deep trench is dug from the well to the house. This will insure that the water line will not freeze. A hole is drilled through the steel casing and a pitless adapter is installed. This is a cast brass part with rubber seals. It allows the pump to be mounted in the well and serves as the connection to pipe the water into the house. The water line is connected to the pitless adapter and then stubbed through the wall of the house. A conduit is also laid in the trench to supply power for the pump. This wire comes into the well through the top of the casing.

The next step is to install a holding tank. This is a tank to provide pressure in the house, with a switch to regulate the pump. When the pressure in the tank drops due to water being used, the switch tells the pump to start. When the tank becomes pressurized, the switch tells the pump to stop. The tank is then connected to the plumbing in the house.

It’s important to maintain the water system, and a good idea to have a professional check the system on a yearly basis. The Carbon County Groundwater Guardians can provide homeowners with further information on maintaining water wells and septic systems.