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Environmental Health – Water Supply

Individual Wells
Use and Occupancy Approval
Certificate of Potability
Water Sample Requests
Well Contamination/Investigations
Well Disinfection
Water Disinfection Devices
Sealing Abandoned Wells
Drinking Water Standards
Public Water

Individual Wells

For property in Carroll County that is not served by public water supply, individual on-site wells are needed to provide potable water. Most well construction today is done by drilling a 10-inch bore hole 100 feet or more below land surface until a sufficient quantity of water is encountered. Plastic or metal pipe (casing) is inserted into this bore hole so as to extend at least 2 feet down into bedrock. At least 8 inches of the well casing must extend above finished grade. The space between the bore hole and the casing is then filled with grout (Portland cement or bentonite) to prevent surface contamination from polluting the groundwater. A sealed and vented well cap is placed on the well head, a pitless adapter is installed through the casing, and a well identification numbered tag is installed on the casing. The well yield is verified by a pump test performed by the driller. This testing procedure lasts from three to six hours, depending on the yield and requires well drillers to record the pumping rate and water every fifteen minutes. A minimum yield of one gallon per minute for six hours and five hundred gallons available (including yield and storage) in a two hour period is required to obtain a residential building permit. Copies of the yield tests are submitted to this bureau for approval and are available to the public upon request. Applications for a permit to drill a well must be submitted to the Carroll Health Department by a licensed well driller. A site plan is also required to be submitted by the applicant. Proposed well locations must be:

  • At least 100 feet (200 feet if directly downgrade) from all existing and proposed sewage disposal systems/areas.
  • At least 100 feet from other sources of contamination (cemeteries, petroleum product storage, etc.).
  • At least 10 feet from property lines.
  • At least 15 feet from roads or dedicated rights-of-way.
  • At least 30 feet from a building foundation

This Department must be contacted to conduct a final construction inspection and approve the well prior to it being placed into service as a private potable on-site water supply.

Useful Information About Your Well Brochure

Use and Occupancy Approval Procedures

The following is a list of conditions that must be met for the Carroll County Health Department to issue approval for a Use and Occupancy permit:

  1. Well Completion Report Approval: The completion report must be submitted by the well driller and be reviewed and approved by the Health Department Staff. Items such as minimum well yield (1 gallon per minute), well casing depth, and grout depth are evaluated.
  2. Final Inspections: Both the well and septic system final inspections must be completed and approved by Health Department Staff.
  3. Water Sample Review: A safe water sample for bacteria, nitrates, turbidity, and sand must be submitted to the Health Department for review. Most often, these samples are collected and analyzed by a Maryland State Certified Private Laboratory due to quicker sample analysis times than the State Laboratory. The following is a list of information that is needed on the sample results sheet:
  • Date, time, location, and tap sampled.
  • Well tag number (CL#).
  • pH, chlorine residual, type of treatment.*
  • Date and time received by Laboratory.
  • Sampler Identification and affiliation.

* When any sample is taken, it must be indicated on the results that the premises were inspected for treatment devices and the type (if any) found should be listed.

After the above conditions have been satisfied, the Health Department will issue approval for a Use and Occupancy permit. At the same time, an Interim Certificate of Potability is issued, allowing the homeowner to put the water supply into service. An Interim Certificate of Potability indicates that the water supply meets minimum well construction and water quality standards. Follow-up sampling is later conducted by the Health Department for the issuance of a Certificate of Potability.

Certificate of Potability

Sometime beyond 30 days (but usually no later than 6 months) of the issuance of an Interim Certificate of Potability, the Health Department will collect water samples from your home. These samples are collected so that a Certificate of Potability may be issued.

To receive a Certificate of Potability, the following criteria must be met:

  1. The well must be properly constructed: Before any water samples are collected, Health Department Staff inspect the well head to ensure it continues to meet well construction standards. Many times after the final inspection of the well, work is done which may not be in compliance with proper well construction standards. If your well does not meet those standards, no samples will be taken until the problem is corrected.
  2. Water sample results must be bacteriologically safe: The only water sample normally taken for a Certificate of Potability is for bacteria. These results must be safe for a Certificate to be issued. If the results are unsafe, it is then necessary to obtain at least 2 consecutive safe bacteriological samples at least 30 days apart. Usually, well disinfection is required in these cases. Sometimes, it may be necessary to investigate to attempt to find the source of contamination.

Requests for Water Samples

The Health Department receives many requests from homeowners, tenants of rental properties, etc. for water samples. The health department does not collect drinking water samples from private homes unless there is a doctor’s diagnosis in order to prioritize resources efficiently. When a doctor diagnoses a patient with a waterborne illness, it signals a potential problem that needs immediate attention. In such cases, the health department steps in to investigate the water quality at the patient’s residence to identify and address the source of contamination.

Private laboratories offer an alternative solution for individuals who want to test their drinking water quality, whether or not there’s a doctor’s diagnosis. These labs provide a range of water testing services, from basic packages to comprehensive analyses that cover a wide spectrum of contaminants.

The Health Department does not sample properties where springs or improperly constructed wells are used as the water source. Results of samples collected from these supplies are known to be unreliable.

The Health Department has no requirement that properties being transferred meet any drinking water standards. Therefore, we do not collect drinking water samples for requests involving real estate transfers. If you wish to have your drinking water analyzed for the purpose of buying or selling real estate, it is recommended that you consult with a Maryland State Certified private laboratory. The Health Department can provide you with a list of local laboratories.

If you have water results from a private lab and have some questions about them please feel free to contact us to discuss your results.

Well Contamination/Investigations

When a water sample result indicates the supply is contaminated with bacteria, it means that the water sample contained coliform bacteria or coliform and fecal coliform bacteria. Fecal coliform is a serious concern because it indicates that the water has been contaminated with human or animal waste. Normally, the Health Department recommends that the well be properly disinfected. Sometimes this is not effective despite several attempts. In these cases, we may investigate to try to find the contamination source. Normally, our investigations proceed in the following order:

  1. Evaluation of Well Construction: The well head is evaluated by staff. Any construction deficiencies are noted and recommendations to bring the well into compliance with current well construction standards are given.
  2. Evaluation of Casing Integrity: A small hole is dug in close proximity to the well casing. Dye is introduced into the ground. The homeowner collects samples from a tap for several days. Samples are then analyzed at the Health Department for evidence of dye in the drinking water. Presence of dye in the drinking water would indicate that surface water is entering the well (either through the pit less adapter or at the base of the casing through the annular space). If this is the case, corrective action would be recommended by the Health Department.
  3. Dye test of on-site sewage disposal system: Dye is introduced into the septic system by flushing dye down a toilet in the house. The homeowner collects water samples from a tap in the house for several days. Samples are analyzed at the Health Department for evidence of dye. Presence of dye would indicate that the on-site sewage disposal system is contaminating the well. If this is the case, corrective action would be recommended by the Health Department.
  4. Tests of other systems: If all options are exhausted on the property, potential sources of contamination not on the property may be investigated. Investigations generally take a significant amount of time. The source of contamination is not always located. Sometimes, it is recommended that a new well be drilled. It should also be noted that most types of well contamination can be treated. However, treatment is not acceptable for fecal coliform bacteria contamination unless there is no other alternative. All treatment equipment must be installed by a licensed plumber. A permit is required through the Carroll County Office of Permits and Inspections.

Well Disinfection

Following are the instructions the Health Department sends to homeowners who need to disinfect their well. These instructions should be used to disinfect after a positive bacteria sample, after replacing a well pump, or after doing any other work to the well:

Method for Disinfection of Water Supply

Chlorinating is an important step in making your water supply safe for human consumption. The Procedure for chlorinating is as follows:

  1. Turn off the circuit breaker for the hot water heater, or in the case of a gas water heater, turn the water heater to pilot. Remove the well cap, or for and older well, remove the vent plug in the sanitary seal.
  2. Add two (2) ounces (by weight) of calcium hypochlorite tablets (preferred) or granules (also known as swimming pool shock) directly to the well. These can be obtained where pool supplies are sold. Do not use slow release chlorine tablets designed for swimming pool chlorine feeders.
  3. In addition, use three (3) ounces of fresh 5.25% household bleach for every ten (10) feet of water in your well. Use a minimum of one-half (1/2) gallon. If you cannot find tablets or granules, increase the amount bleach by 50% (i.e. 100 oz. increase to 150 oz.). Dilute the bleach with a gallon of water. Pour the mixture directly into the well, making sure the solution coats the inside of the casing. In some older wells, the chlorine solution may have to be added through the vent plug on top of the sanitary seal.
  4. After the chlorine has been added, wait thirty (30) minutes, then run the water using an outside faucet until there is a chlorine smell. If chlorine is not apparent after an hour, turn the water off for fifteen (15) minutes, then run the water again for up to one hour, repeating this process until the chlorine smell is present.
  5. Run every faucet until a chlorine smell is detected. This should include hot water taps, outside taps, barn taps, showerheads, and the taps at the bottom of the hot water heater and pressure tank. After the chlorine is detected, close each tap. Any appliances attached to the system such as dishwashers, ice makers, washing machines, furnace humidifiers, etc. should be cycled until chlorinated water has moved through the unit.* When all parts of your water system have been chlorinated, attach a garden hose to an outside tap and run chlorinated water down the well for 1 minute, moving the end of the hose around the inside of the well casing. Discontinue immediately if the water becomes cloudy.
  6. Allow the water to remain in the plumbing system for at least 12 hours. Except for flushing toilets, no water should be used during that 12-hour period. At the end of this period, the chlorinated water should be run off. This should be done intermittently (run water no longer than one hour each time). An outside tap with an attached hose directed away from the house should be used, if possible, to prevent overloading the septic system. You should continue this process periodically until no chlorine smell is present. This process may take several days. The chlorine concentration will initially be very high, and it is strongly recommended that people refrain from using the water for bathing or laundry until the chlorine odor is gone.
  7. When you finish, contact the Health Department for a follow-up water sample. The Health Department will normally require a 14-day waiting period after chlorination, before a follow-up water sample will be taken. This is to ensure that the sample is representative of the normal condition of the water supply.  The water supply should be considered unsafe until it has been sampled and determined to be safe by the Health Department or another State-certified lab.
    * Please, consult with a plumber or other water service technician before disinfection of any water treatment equipment.

Well Disinfection Checklist

Water Disinfecting Devices

Use of an ultraviolet device or a chlorine injection system as a means of disinfecting water to meet bacteriological requirements is acceptable only under certain circumstances. Each case is reviewed when a written request for permission to use such equipment is received by the Health Department.

An ultraviolet disinfection device does not change the chemical or physical characteristics of water. Certain characteristics of water (turbidity, color, and organic impurities) may impair the effectiveness of an ultraviolet device. Therefore, additional treatment may be required. Ultraviolet treatment does not provide residual bactericidal action. Some maintenance is required.

The injection of chlorine into a water supply at the point of entry into a building ensures residual bactericidal action throughout the water distribution system. This system requires more maintenance than an ultraviolet device but may be necessary where plumbing problems are suspected or known to be contributing to the contamination.

Health Department requirements for both types of treatment systems are described below. Installation permits are required by the Carroll County Bureau of Permits and Inspections.

Requirements for Ultraviolet Disinfection Units on Water Supplies:

  1. The unit shall be designed to permit the user to clean the water contact surface of the jacket.
  2. An automatic flow control valve, accurate within the expected pressure range, shall be installed to restrict flow to the maximum design flow of the treatment unit.
  3. An accurately calibrated ultraviolet intensity meter, properly filtered to restrict its sensitivity to the disinfection spectrum, shall be installed in the wall of the disinfection chamber at the point of greatest water depth from the tube or tubes.
  4. A flow diversion valve or automatic shut-off valve shall be installed which will permit flow into the potable water system only when at least the minimum ultraviolet dosage is applied. When power is not being supplied to the unit, the valve should be in a closed (fail-safe) position which prevents the flow of water to the potable water system. THERE CAN BE NO BY-PASS OF THIS VALVE (This includes any by-pass switch built into the valve).
  5. A valve to allow sampling of the water supply prior to treatment must be installed if it is not already present.
  6. Ultraviolet radiation at a level of 2,537 Angstrom units must be applied at a minimum dosage of 16,000 microwatt-seconds per square centimeter at all points throughout the water disinfection chamber.
  7. Maximum water depth in the chamber, measured from the tube surface to the chamber, shall not exceed three inches.

Requirements for Chlorine Injection Systems on Water Supplies:

  1. A retention (blending) tank that will allow the water to have a minimum of twenty minutes contact time with the chlorine must be included in the installation. For residential applications, a 120-gallon retention tank should be adequate. Sizes for commercial applications are determined on a case by case basis.
  2. A valve to allow sampling of the water supply prior to treatment must be installed if it is not already present.
  3. The residual chlorine level must be maintained between 0.5 and 1.0 ppm.


Sealing Abandoned Wells

Carroll County, while considered part of the greater Baltimore Metropolitan area, still retains much of its rural character. A prime example of this is the number of wells which provide our homes and businesses with drinking water. Between 40% and 50% of the residences in Carroll County employ individual wells, far above the number in the other metropolitan counties, which have considerably more homes and businesses on public water systems. However, this figure could approach 70% if one considers that a number of Carroll’s public water systems derive their supply from large production wells.

Generally, there is no real problem with so many wells. Modern regulations regarding well construction and state of the art well drilling techniques ensure a safe and abundant supply of drinking water for many years and that the groundwater will be protected.

That is, unless a well must be replaced because of drought or the community hooks up to a new public water system, such as a number of communities in Carroll County have done in the last decade or so.

Wells that are taken out of service are deemed “abandoned” and generally must be sealed properly by a licensed well driller. The sealing process usually involves filling the bedrock portion of the well with stone or concrete and capping the upper portion with concrete. If a well is not sealed, or sealed properly, the abandoned well can become a conduit for contaminated water on the ground surface to flow down the well into the water aquifer and possibly contaminate other residents’ wells in the area or even wells distant to the abandoned well. This is why the Carroll County Health Department works with residents to properly seal their abandoned wells. Most, if not all of us, would not want to be responsible for making someone else’s well water unfit to use. But many homeowners do not understand how their abandoned well could possibly cause a problem for someone else, hence our education efforts.

It is possible to maintain a well on your property which no longer provides your home with drinking water. The well water must test safe for bacteria; it must not interfere with the replacement of a septic system; it must not pose a safety hazard; it must be a drilled well that meets current construction standards (no hand dug wells) and it must be physically disconnected from the house. Some homeowners choose to do this for lawn/gardening watering or for other non potable purposes.

While abandoned wells do not capture the interest of a communicable disease outbreak or of preparing for a bioterrorism attack, the proper sealing of these type wells is nonetheless important to the protection of the health of the public.

Public Water Supply