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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.
Introduction to Groundwater Wells
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as it is withdrawn).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.
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Introduction to Septic Systems
The image above shows a house with a private septic tank and drainage field.
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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.
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.
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.
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Well and Septic System Testing and Permitting
When a property owner has a well or septic system installed for use on the land, the owner wants assurance that those utilities 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 311.
Well Testing and Permitting
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 Well and Septic Section
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, 1pp, 25K)
Find additional information on how to apply for the water use permit (PDF, 1pp, 150K)
Septic System Testing and Permitting
Before any formal testing occurs, the DPS Well and Septic Section 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.
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Additional Requirements for Large-Capacity Wells and Septic 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 MDE 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.
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Well and Septic System Maintenance
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, Water Wells, and Water Contamination (PDF, 12pp, 313K)
This publication starts with the basics of how water, in its varying states, moves through and interacts with the environment, with a strong focus on groundwater and wells. It continues with information on how we can protect our water supplies.
- Well Records and Maintenance Guidelines (PDF, 6pp, 190K) and
Septic Records and Maintenance Guidelines (PDF, 6pp, 385K)
These two documents provide information on well and septic system components and how they work. They include suggested methods for keeping records of your on-site systems, as well as useful recommendations on maintaining your well and septic system.
The County’s Department of Permitting Services also has information available for septic system records and maintenance which adds to the information provided by the Maryland Cooperative Extension. Please use this link to refer to the DPS Septic Records and Maintenance Guidelines document.
Well and Septic System Problems
Who Should You Contact When Problems Occur?
Contact Department of Permitting Services, Well and Septic Division
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