For most of the first 25 years of our marriage we lived in rental apartments. We talked about someday owning a house. My husband wanted a big house on lots of land in Virginia, his home. I generally dreamed of a house of more modest size near whatever city we were living in at the time. After living a decade and a half in California with constant water restrictions and crisis, water became the number one item on my list (followed by high-speed internet). So, we ended up in Virginia in his someday house with a well with my water supply.
There is a whole lot beyond being clear and tasting good that makes water satisfactory. The first thing to verify is that the well is constructed properly. That is fairly simple, though there are no national standards for construction of private water wells, in Virginia the Department of Health well construction regulations went into effect in 1992. So, buy something with a well drilled after that. A simple trip to the local health district allowed me to get the well completion report for all the houses we were considering. Well built to current standards-check.
The well completion report tells you how old the well is, how deep, what the well yield was at completion. I was also looking for a well with a stabilized yield greater than 6 gallons a minute in the right kind of geology because geology impacts how a well ages. If you are buying an older well (still built after 1992) check the water level and yield - yield diminishes over time. You will have to hire a well driller to do this.
There are three considerations for a private well- the well and well system, the water quality and the water quantity. Failure in any of these can impact your life and the value of your home. The well is essentially a hole in the ground. Shallow wells (those less than 50 foot deep) are dug or bored into the ground and have larger diameters (2-4 foot). Shallow wells are more prone to contamination and drought and bored wells have the shortest life. Deeper wells are called drilled wells because they are drilled into the ground to depths from 50-450 feet or more and because of the need for drilling rigs cost much more to build. The diameter of a drilled well is 6-8 inches.
Only buy a home with a drilled well. Generally, drilled wells provide a safer source of drinking water, and are less often impacted by drought. In igneous and metamorphic rock systems like the Piedmont of Virginia, the fractures and fault lines formed in the rocks store and transmit groundwater. The size and number of water bearing fractures varies and there is a wide variation in well yields from under 1 gallon per minute to over 50 gallons a minute depending on location and specific site geology. Fractures can become fouled with mineral deposits or iron bacteria or simply go dry over time.
Aquifers can go dry unexpectedly, but all wells will fail over time. The lifespan of a drilled well is assumed to be 20-50 years, but varies tremendously based on site specific conditions. I personally know of a drilled well that lasted 65 years, but if you are buying a home with a well over 20 years old you will need to budget for drilling a new well. Make sure that the cost is considered and that the property has another location to drill a well.
The well system consists of the well, the well casing, the inlet for water, and the pumping system. The casing is the structure around the well hole to prevent its collapsing. It could be a steel or plastic casing or an open hole in the bedrock. In this part of Virginia, the Piedmont, the top of the well is lined with steel for 50 feet and then the well is open in the bedrock allowing the water to flow into the well. A steel well casing will rust over time and eventually collapse. The well casing should be 1-2 feet above the land surface to make sure that during storms and flooding that nothing washes down the well. There should be no holes or cracks in the visible portion of the casing and the well cap should be tightly bolted closed.
The essential components of a modern drilled well system are: a submersible pump, a check valve (and additional valve every 100 feet), a pitless adaptor, a well cap, electrical wiring including a control box, pressure switch, and interior water delivery system. There are additional fittings and cut-off switches for system protection, but the above are the basics and each and every component must work properly for your well to function properly.
The pumping system includes the pump, piping and electrical connections to pump water from the well into the house and a pressure tank to maintain constant water pressure in the house. Shallow wells usually use centrifugal pumps and are often located in a pump house or the basement. Drilled wells have submersible pumps. The pump and pumping systems are the most likely components to fail in a well. The average life of a submersible pump is variously reported as 12-15 years, but many pumps fail in the first few years.
In addition, in order for a well to keep supplying water to your home the components within the basement must all continue to work. These components provide constant water pressure at the fixtures in the house and the electrical switch that turns on the pump. For a drilled well if there is any other equipment beyond the pressure tank, it is a water treatment system, and you need to test the water before and after the treatment.
The pump moves water to the basement water pressure tank, inside the tank is an air bladder that becomes compressed as water is pumped into the tank. The pressure in the tank moves the water through the house pipes so that the pump does not have to run every time you open a faucet. Bladders and electrical switches will fail over time and valves and switches and impellers on the pump can break, foul or find any number of ways to fail. You have to assume that pump systems that are older than 12 years are on borrowed time. It does not mean that a pump system cannot last 25 years or more, but I would not bet on it.
When buying a home with your own water supply you need to consider the construction, condition, age and location of the well in addition to water quality and quantity. Geology plays an important role in the water quality and quantity. Clay loams or silty clay soils filter pollutants and protect an aquifer. A shallow water table and fractured bedrock may provide larger quantities of water, but the shallow fractured rock systems are susceptible to contamination from the surface.
The specific geology and water quality will determine the life span of a well. So pick your desired geology. Within the three counties around here there are significant variations in the geology. There is an area in Loudoun County that is high in iron and an area nearby that is karst terrain. The groundwater in karst terrain is easily impacted by surface contamination and is potentially subject to sinkholes. No. There are areas with very high natural iron and manganese content, areas of extremely hard water and areas with soft or aggressive water. No, no and no.
Within Prince William County Virginia there are several distinct geologic provinces that will have different groundwater characteristics. The northwestern part of Prince William County down the hill from Bull Run Mountain, consists of sedimentary rocks of the Culpeper Basin. The predominant rock types are conglomerates, sandstones, siltstones, shales, and argillaceous limestones. This geology tends to have moderate to excellent water-bearing potential because it is a fractured rock system with very little overburden. The highest reported yields in the county are from wells in this geology. In other parts of the county there are deep wells in the diabase that tend to have reliable lower yields. I choose fractured siltstone as my targeted geology.
The issue of whether water is safe to drink is separate from whether the water is free of unpleasant contaminants like iron, manganese, chloride, and low levels of hydrogen sulfide or the groundwater has been contaminated. The well must be tested. Before you buy test the water for all primary and secondary contaminants in the Safe Drinking Water Act. In addition to testing the water for any nearby likely sources of contamination. I was only interested in purchasing a home with water that did not need any treatment. There is a big difference to me between fixing a problem that develops over time and buying that problem.
Water chemistry is a tough category to give rules of thumb. Your best option is to do a broad scan of the well water quality. There are screening packages available from U.S. EPA certified laboratories like National Testing Laboratories that screen water wells for all the primary and secondary contaminants in the Safe Drinking Water Act.
The WaterCheck with pesticides package from National Testing Laboratories is a broad stroke test, testing the water for 103 items including Bacteria (Total Coliform and E-Coli), 19 heavy metals and minerals including lead, iron, arsenic and copper (many which are naturally occurring, but can impact health); 6 other inorganic compounds including nitrates and nitrites (can indicate fertilizer residue or animal waste); 5 physical factors including pH, hardness, alkalinity; 4 Trihalomethanes (THMs) and 47 Volatile Organic Chemicals (VOCs) including Benzene, Methyl Tert-Butyl Ether (MTBE) and Trichloroethene (TCE). The pesticide option adds 20 pesticides, herbicides and PCBs. This testing can be done for a few hundred dollars.
The report they produce tell you if the contaminant was detected, if detected if it was below or above the EPA standard under the Safe Drinking Water Act, and finally if the contaminant was above the standard if it was above an enforceable MCL (maximum contaminant level). If sodium is present it should be under 10-20 mg/L. Any higher and you have salt water infiltration or the well system might have a water softener that is obscuring many of your results and you need to test again ahead of the water treatment. The nitrate level should be well below the EPA standard of 10 mg/L closer to the background level (around 2 mg/L in northern Virginia). Higher than 5 mg/L tends to be related to septic performance either at your house or a neighbors but can also indicate historic use of fertilizers or animal waste storage. If these problems exist, it will only grow worse with time.
I like hard water so anything between 100 mg/L and 180 mg/L is fine by me. Higher though, could be difficult to live with and should be avoided. Too low and you might have aggressive water (slightly acidic) which has a whole bunch of other problems or once more a water softener is installed and you need to retest.All trihalomethanes, solvents (organic volatiles) and hydrocarbons should be non-detect. None of these are naturally occurring and even low levels are an indication of a source of industrial contamination. A trace of TCE in a well was the first symptom of what turned out to be a Superfund site in Loudoun County. Run away. Same is true for the pesticides and other organic analytes.