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Private Well and Septic Service

When your property uses a well for water supply and a septic system for wastewater disposal, you essentially become your own sanitary utility. You own and operate the facilities, maintain them, and have to replace them when necessary. 

Your water supply system is the well drilled into your yard, which taps into the groundwater under your property. Your wastewater disposal system is the septic system buried elsewhere under your yard. The septic system treats wastewater from your home or business and disperses treated effluent into the soil.

The ability of these private systems to provide fresh water and dispose of sewage depends on the soil and rock conditions under your property and on how well you maintain and operate the systems.


Problems with Your Well or Septic System?

Need assistance or guidance with your well or septic system?  Contact the Department of Permitting Services



Groundwater Wells

Graphic of a groundwater well

A well uses the groundwater in the rock under your property as a water supply. The system typically includes a narrow well (usually about 6 inches in diameter) with a submersible pump that connects directly to a home or business. 

The well is drilled to a depth below the level of the water table so that the well shaft can store water for periods of high water demand. An impervious sleeve lines the upper part of the well shaft to prevent surface water and shallow groundwater from entering, which might contaminate the well water supply. As the pump removes water from the well shaft, groundwater flows in to replace what has been used (although not necessarily as quickly as it is withdrawn).

Depending on the volume of water required, you might also need on-site water treatment and an aboveground storage/pressure tank. Current standards require that you identify two reserve well sites for future use in the event of a well failure. Wells must be sited at least 100 feet from any existing or proposed septic system.


Private Well Frequently Asked Questions

Graphic of the groundwater table and the recharge process.


What is groundwater?
Groundwater is water held in the cracks and other spaces in layers of rock and sand, deep underground in an aquifer. When it rains or snows, some water flows into lakes and streams, some evaporates back into the air, and some water seeps into the ground. This water infiltrates the upper soil layers and eventually reaches the saturated zone of the aquifer, where all the interconnected openings between rock particles are filled with water.


How does the water get into my well?
An aquifer is much like a giant sponge, and your well taps into the water being held in the "sponge." Groundwater flows slowly through the pores and fractures in the aquifer rocks, keeping your well full of fresh, naturally filtered water. The cycle of rain, evaporation, and infiltration continually replenishes the groundwater and keeps your well saturated.


Is my water supply at risk due to drought?
The drought years of 1997, 1998, and 1999 raised the consciousness of many well users about the limitations of their water supply. Drought and the associated lack of groundwater recharge affects water supply in three ways:

  • A lowered water table means that there is less storage available in the well borehole. Depending on depth of the well and water usage, you may experience loss of water pressure or water from the well.
  • Mineral precipitation may occur in the upper fractures of the borehole; when the drought is over, well recharge may not be as great.
  • If your well is old and/or shallow, and the drought severe enough, your well may lose water completely.

It is always important to conserve water, but during a drought you should take special care to limit your water use!


What is wrong with the smell/taste/appearance of my water?
Common problems with well water include cloudiness, the odor of rotten eggs, or a salty taste; occurrences such as these are often natural, and not a result of contamination. These characteristics are not usually harmful to human health, but if there are abnormal characteristics or sudden changes in water quality, you should test your water, and, if needed, have the well examined by a qualified scientist.


Do I need to test my well water?
Your well should be tested once a year, or more frequently if you suspect a problem. Also, testing should be done whenever:

  • work is done on the well;

  • if there is a notable change in water taste, smell, color, or clarity;

  • if neighbors discover a contaminant in their well water; or

  • if there is an unexplained illness in humans or animals.

Water should be tested by a certified, qualified, public or private lab. At a minimum, test water for bacteria and nitrates, in addition to any contaminants likely on your property. A good initial set of tests for a private well includes hardness, alkalinity, pH, conductivity and chloride. Contact DEP for testing suggestions based on your location and risk. A visual interpretation of the water samples, as well as taste and odor tests, can provide valuable clues about possible contamination. 


How can well water become contaminated?
There are two types of contaminants: those occurring naturally, including minerals such as iron, calcium, and selenium; and those produced or introduced by human activity. The groundwater a well draws from can be affected by human contamination, either by substances seeping down through the soil layers from the top surface, or by substances entering directly underground from such things as leaky storage tanks, mining, or septic systems.


What are the most common causes of contamination?
A major cause of groundwater contamination is outflow from septic systems and cesspools. Improperly designed or maintained structures often leak into the aquifer, introducing bacteria and viruses into the water source. Liquids leached through storage ponds and landfills, carrying dissolved waste materials like heavy metals and organic decomposition products, are also frequent contaminants. Other contamination often comes from pesticides and fertilizers.


What do I do if my water is analyzed as unsafe?
First, resample and retest to be sure the water actually is contaminated. Then, try to find the source of the contamination, such as a cracked well cover or a nearby chemical spill. For assistance in identifying potential contaminants, contact DEP. After the contamination is controlled, disinfect the well system yourself or hire a professional.


What are the advantages to having my own well?
A well on your property provides you and your family with pure water directly from the source. There are no added chemicals or treatment, and you don't have to worry about the cost or reliability of public infrastructure. Groundwater is a renewable source of drinking water, relied on by 80,000 residents of Montgomery County.


How do I maintain my well?
Careful attention to activities at the surface, along with minor maintenance efforts, will keep your well providing clean water for many years. There are a number of responsibilities you have as a well owner:

  • Periodically inspect the well cover and casing for wear, holes, and proper fit.

  • Make sure that the ground slopes down, away from the well, for proper drainage.

  • Take care when working or mowing near the well, and keep the area clean and accessible.

  • Keep hazardous chemicals (pesticides, fertilizers, gasoline) away from the well, and prevent spills or dumping of any harmful substance in the area.

  • Always use state licensed well diggers or pump installers when servicing your well, and be sure to abide by state and county regulations.

  • Test water annually, and keep a record of the results, along with records of well maintenance and conditions.

  • Dispose of chemicals and hazardous substances appropriately: don't flush, dump down drains, or dump on the ground! Call Solid Waste Services (311) for details on proper disposal.

  • Clean up any oil, gasoline, pesticides, fertilizers, or household chemical spills as thoroughly and as quickly as possible. If necessary, call the Fire Department (911) or DEP (311) for help.

  • Minimize your use of fertilizers and pesticides, and encourage your neighbors to do the same. These substances can easily seep into groundwater through the soil layers, where collective accumulation can lead to unhealthy levels.

  • If you have an old well on your property, make sure it is properly closed and capped. Abandoned wells are a direct connection to the aquifer, providing an easy means of contamination.

  • Underground storage tanks are a common cause of groundwater contamination. Be aware of the condition and location of septic or fuel tanks, and keep your septic system pumped and inspected.



Maryland Department of the Environment

EPA's Private Drinking Water Wells
Approximately 15% of Americans obtain water from their own private drinking water supplies. Most of these supplies are drawn from ground water through wells, but some households also use water from streams or cisterns. EPA does not oversee private wells, although some state and local governments do set rules to protect users of these wells. EPA encourages these households to take special precautions to ensure the protection and maintenance of their drinking water supplies.

Safe Drinking Water Hotline
The Environmental Protection Agency's Safe Drinking Water Hotline provides the general public, regulators, medical and water professionals, academia, and media, with information about drinking water and ground water programs authorized under the Safe Drinking Water Act. The Hotline is operated under contract by Outreach Process Partners, LLC and housed in its Annapolis, MD offices.

Best Management Practices for Wellhead Protection (.pdf, 279KB))
University of Idaho College of Agriculture

American Ground Water Trust
National Ground Water Association


Septic Systems

A septic system treats and disposes of wastewater. The system includes a septic tank connected directly to your building. Current regulations require two-chamber septic tanks that hold up to twice the daily maximum expected flow from the user. The tank design allows sewage solids to separate from liquids and settle to the bottom of the tank. Every two to five years, a contractor needs to remove the solids from the tank. 

The liquid from the upper level of the tank flows into an underground drainfield—a network of gravel and sand-filled trenches that use pipes to distribute the effluent across a broad area into the ground. Bacteria in the soil below the drainfield provide the final step in the treatment process as the effluent percolates down through the soil and finally into the water table.


How Much Area is Needed for a Septic System?

Graphic of septic tank

Under current standards, a septic system must have an initial drainfield and enough area for three reserve or back-up drainfields. These back-up fields are built and put into service only as the drainfield in use fails. A typical single-family house needs an area of at least 10,000 square feet (slightly less than one-quarter acre) for the initial and reserve drainfields.

Properties in the Patuxent River watershed, with water supply reservoirs for the Washington Suburban Sanitary Commission, must reserve an additional 70 percent of treatment area. That means a single-family house that needs to reserve 10,000 square feet elsewhere in the County would need to set aside 17,000 square feet (slightly less than two-fifths acre) in the Patuxent River watershed. 

Septic systems may not be located closer than 100 feet to any existing or proposed well. In addition, County regulations establish other septic system setbacks for site features like steep slopes, stream buffers, and buildings.


Types of Septic Systems

Most septic systems in use in the County are deep-trench systems, in which drainfield trenches about two feet deep are buried at least two feet under the soil surface.

An alternative to the deep-trench system is the sand-mound system, where the drainfield is artificially elevated above the natural soil surface to overcome a shallow water table or a marginal percolation rate in deeper soils.

Older on-site systems use several varieties of discharge methods, such as seepage lagoons, dry wells, and seepage pits. These older systems are allowed to serve only existing structures provided they continue to function adequately. Under the County's current on-site system regulations, new construction (a new structure or a significant expansion of an existing structure) may use only deep-trench and sand-mound septic systems.




Just as public sanitary utilities must monitor and maintain their water supply and wastewater disposal systems, a property owner needs to perform periodic maintenance and testing of private on-site wells and septic systems. This helps to ensure the maximum life of the systems, reduce replacement and repair costs, and protect the health of users and the environment.

The Maryland Cooperative Extension has prepared several useful documents that address these subjects. Anyone who uses or contemplates using a well or septic system should review and pay heed to the tips, recommendations, and sound advice in the following documents:

  • Water Wells and Their Maintenance Guidelines
    Introduction: “If you have a home well, you alone are responsible for maintaining the safety of your drinking water supply. When your well system is suitably located, correctly installed, properly maintained, and regularly tested, you will have few problems with water quality. Water testing may be required by lenders when you sell or refinance your home, but otherwise, it's up to YOU to make sure it is safe to drink.”

  • Septic Records and Maintenance Guidelines  (PDF, 381K)
    Introduction: “Proper design, installation, and maintenance of your septic system will maximize your system's life. It will prevent failures that can be unsightly, foul-smelling, and threatening to your family's health. Good maintenance reduces the risk of contaminating your well water, and may save you from costly repairs or system replacement.  Septic tank inspection may be required by lenders when you sell or refinance your home. The repair of a failing system is usually a cost to the seller. So, ignoring your septic system will not save money in the long term!”



Testing & Permitting

When a property owner has a well or septic system installed for use on the land, the owner wants assurance that they will function adequately and provide service for a reasonable length of time. The testing and permitting requirements established by the County's On-Site Systems Regulations ensure that, at least when wells and septic systems are installed, that purpose is accomplished.

In Montgomery County, the Department of Permitting Services (DPS), acting on behalf of the Maryland Department of the Environment (MDE), has the responsibility of testing for and permitting wells and septic systems. (Note that in other Maryland jurisdictions, the Health Department often carries out this function.)

The discussions below on the testing and permitting processes for wells and septic systems provide only general background information. The DPS Well and Septic Section Web site has testing and permitting requirements and applications. They may be reached by phone at 3-1-1.


What is Required for Wells?

In most areas of the County, groundwater is reasonably plentiful as long as you drill deep enough to find it. As a result, DPS doesn't usually require testing before it issues a permit for drilling a water supply well. However, the agency does need to approve an on-site system plan before issuing a permit.

Flow testing is required after drilling and before a building permit is issued to ensure that the well can pump an adequate flow of water. The state's minimum flow requirement for approving a new well for use is 1 gallon per minute (GPM). (Keep in mind that though allowed, 1 GPM is a low flow rate that requires spacing out typical high-volume water uses, such as bathing and washing clothes and dishes, throughout the day.) The DPS staff can advise well permit applicants about special requirements, including the areas of the County where prior testing is required for a permit.

The MDE Water Management Administration's Water Supply Program requires some multiple-unit residential projects and nonresidential projects using groundwater wells to apply for and obtain a water appropriation and use permit. You can contact the MDE by phone at 410.537.3714 or 1.800.633.6101.

Download a copy of the MDE water appropriation and use permit (PDF, 25K)

Find additional information on how to apply for the water use permit (PDF, 150K)


What is Required for Septic Systems?

Before any formal testing occurs, the Department of Permitting Services needs to review and approve a layout plan for the site showing proposed testing locations. Following this step, testing for new septic systems occurs in two stages—a water table test and a percolation test.

Water Table Testing:

The first test, the water table test, determines the depth to the groundwater—saturated soil under the property. The unsaturated soil between the bottom of the drainfield trench and the top of the water table provides area for treating the wastewater effluent. If sufficient depth—approximately four feet-between these is not maintained, untreated wastewater effluent might enter the water table and could contaminate water wells or streams and ponds. The level of the water table fluctuates throughout the year. Note that this test is conducted only in the late winter to early spring when the water table is known to be at its highest level. If low rainfall conditions have occurred throughout the preceding year, the DPS Well and Septic Section may chose to shorten the usual testing period.

Percolation Testing:

The second test, the percolation test, determines how quickly wastewater effluent will move downward through the soil. You need to complete and satisfy water table testing before moving on to percolation or "perc" testing. If the flow rate though the soil is too fast, the effluent won't stay in the soil long enough for adequate treatment, again allowing untreated wastewater into the water table. If the flow rate is too slow, the soil won't accept and distribute effluent flows from the drainfield quickly enough. Eventually the septic system will back up to the yard above the system or into the user's building. As you might expect, either situation creates public health problems.



Large-Capacity Systems

The County uses the Water and Sewer Plan to approve and inventory wells and septic systems with larger capacities than would be expected for an average or even a substantially larger-than-average single-family house. These larger on-site systems have the potential for more substantial effects on the surrounding environment than a low-density residential use. The County also looks at where these larger systems start to cluster with an eye toward potential cumulative effects from large-capacity systems.

The state categorizes these larger-capacity facilities as "multiuse" water supply and wastewater systems. In Montgomery County, the multiuse designation applies to on-site systems with a maximum (or peak) design capacity of 1,500 or more gallons per day (GPD). By comparison, a typical four-bedroom single-family house would have on-site systems designed for approximately 600 GPD. The Maryland Department of the Environment imposes additional permitting and management requirements on multiuse systems with a peak design capacity of 5,000 or more GPD.

The users of multiuse systems are usually in the rural portions of the County, outside the limits of the planned public water and sewer envelopes. These users typically include:

  • Commercial buildings such as small shopping centers, grocery stores, medical offices, and golf courses

  • Institutional facilities such as day-care centers, places of worship, and private schools

  • Public facilities such as schools, fire stations, and park buildings

Multiuse systems are approved through the category change request process. The category change application includes an option to specify a request for multiuse system approval, rather than an actual change of water or sewer category. For applicants who need to pay a category change application fee, DEP adds a surcharge for multiuse systems.