Water Quality

About Our Water Sources

Mount Pleasant Waterwokrs (MPW) has two water sources: groundwater from the Middendorf Aquifer, and purchased waters from Charleston Water System (CWS).

The Middendorf is a large body of pristine groundwater between 1,800 and 2,000 feet deep beneath Charleston, Dorchester and Berkeley counties.  MPW treats the raw water using state-of-the-art Reverse Osmosis (RO) technology.  The treated surface water provided by CWS is from the Bushy Park Reservoir and the Edisto River.


Common Water Quality Concerns


Water Pressure

Water pressure at your home or business can vary depending on the pumping capacity of our high service pumps and/or the water demand on the system.  It can also be affected by the plumbing system within your home or business.

Mount Pleasant Waterworks (MPW) generally maintains a consistent pressure at our pumping stations.  The water enters the distribution system between 55 and 70 pounds per square inch (psi), which is very desirable in a residential application.

During the colder months, a consistent pressure in the system is easily maintained.  During the summer months, water demand can vary dramatically due to outdoor water use.  During high demand periods, the water moves through the mains at a high velocity which results in lower water pressures.  Due to these high demands, you may find that water pressure at your residence is lower during the hot and dry summer days.

Pressure at your home will also be lower if you are using an indoor outlet while a sprinkler system is running in the yard.  Due to the high flow of water through your service line, the pressure at all outlets will drop.  Therefore, it is not recommended that you try to take a shower when the lawn sprinkler is operating.

Water Odors - Chlorine

Water is defined as a tasteless, odorless, colorless liquid.  Odor can be caused by a number of factors in drinking water. Even though there is an occasional odor to our drinking water it remains safe to drink.  Mount Pleasant Waterworks (MPW) performs constant testing to verify the safety of the water from your tap.

Mount Pleasant Waterworks (MPW) occasionally receives questions from customers concerning the smell of chlorine in their water. Maintaining a chlorine residual in water protects public health.

Why Chlorine?

The addition of chlorine to water supplies began in the early 20th century.  At the time it was first introduced, water-borne diseases in this country such as typhoid, cholera and hepatitis were the primary cause of death to most Americans.   The introduction of chlorine to water supplies had a remarkable effect on extending the longevity of human life.

Chlorine continues to be used today to ensure diseases are not spread through the water supply.  MPW adds chlorine to our well water at each Reverse Osmosis (RO) plant and the water we purchase from the Charleston Water System (CWS) is already chlorinated. 

Discolored Water

Water is defined as a tasteless, odorless, colorless liquid.  Color can be caused by a number of factors in drinking water. Even though there is an occasional color to our drinking water it remains safe to drink.  Mount Pleasant Waterworks (MPW) performs constant testing to verify the safety of the water from your tap.

Although the water is not aesthetically pleasing when it becomes discolored due to natural sediments, there are no adverse health effects if the discolored water is consumed.

Rust from Pipes

Water has naturally occurring materials such as iron, silica and calcium in various quantities.  Over time, these materials accumulate inside water mains and internal household plumbing.  If the main water pipe is cast iron, the natural reaction between water and the piping material forms rust inside of the pipe.

On occasion, when the flow of the water inside the water mains or in the household plumbing increases, the sediment will come off the pipes and be carried by the water.  The water tends to appear a yellow-orange color due to the iron oxide (rust). 

If you experience discolored water, be sure to avoid doing laundry. 






Earthy/Musty Odor

Mount Pleasant Waterworks’ customers receive water from two water supply sources:  reservoir and river water (surface water) and deep well (ground water).  The taste and smell of surface water may fluctuate throughout the year due to constant changes in rainfall, temperature and other seasonal variations.  The characteristics of ground water, on the other hand, are very consistent. Since ground water is naturally located deep in the ground; it is undisturbed by the elements that can affect water quality. 

It is a common misconception that clean, safe water has no taste or smell.  Yet, in reality, taste and smell are influenced by the water source, treatment process and temperature.  Sometimes harmless naturally occurring compounds in the water can produce an undesirable taste or smell.  Contrasting compounds can then be added to the water during the treatment process to remove or reduce offensive odors/tastes.

Due to changes in surface water characteristics, particularly during the spring and fall seasons, some customers may detect an earthy/musty smell in the water.  This type of odor is usually associated with the secondary effects of a harmless, natural algae growing in the reservoir.

Water Odors - Hydrogen Sulfide

Water is defined as a tasteless, odorless, colorless liquid.  Odor can be caused by a number of factors in drinking water. Even though there is an occasional odor to our drinking water it remains safe to drink.  Mount Pleasant Waterworks (MPW) performs constant testing to verify the safety of the water from your tap.

Rotten Egg Smell

Occasionally, MPW customers express concerns of a “rotten egg” type odor from the water.  The smell of rotten eggs is usually associated with hydrogen sulfide.  Hydrogen sulfide is formed by sulfur bacteria that may occur naturally in water. These bacteria use the sulfur in decaying plants, rocks, or soil as their food or energy source and as a by-product produce hydrogen sulfide gas. The sulfur bacteria do not cause disease, but their presence in water can cause a bad taste or odor.

"Rotten egg" odors from hydrogen sulfide are sometimes only present in hot water.  This may indicate a reaction with the magnesium rod in the water heater.  Consider either removal or replacment with an aluminum rod as a remedy.  Sometimes hot water will have a "sour" smell, similar to the smell of an old damp rag.  This happens when, in an effort to save energy or to avoid blending hot and cold water, the thermostat of the water heater is lowered.  Odor-causing bacteria live and thrive in warm water and can infest the water heater.  This is corrected by returning the thermostat to its recommended temperature, becuase the odor-casuing bacteria are killed at the higher water temperature (at or above 140 degrees).  Caution: Be sure the water heater has an operable pressure relief valve before increasing the water temperature.  If you want to keep your water heater temperature at a lower setting becuase scalding from hot water is a concern, each time the odor returns, increase the water temperature for a few hours to kill the odor-causing bacteria.  Then flush the very hot water out of the tanke and lower the temperature back to the desired level.

Faucet or Drain?

When people call about the hydrogen sulfide odor, they often times state the odor is coming from the kitchen faucet.  What may be occurring is that food has accumulated in the drain of the kitchen sink and is decaying producing the hydrogen sulfide gas.

When the water is turned on, the water displaces the hydrogen sulfide that has accumulated and the gas rises making the odor more noticeable. 

Because turning the water on initiates this sequence of events, people understandably think the odor is coming from the water.


Water naturally contains small amounts of bacteria.  During the water treatment process many of these bacteria are removed or destroyed during treatment.  Disinfection is the last stage of treatment and is to ensure that bacteria are destroyed and that a disinfectant residual is left in the water to prevent bacterial growth in the distribution system.  Mount Pleasant Waterworks (MPW) uses a combination of chlorine and ammonia gas to form chloramines as the source of disinfectant residual.  Chloramines are more stable and have a longer half-life than chlorine allowing for better protection in the water distribution system.

MPW monitors its distribution system closely, exceeding the required sampling requirements set by the Environmental Protection Agency (EPA) and South Carolina Department of Health and Environmental Control (SCDHEC).  MPW monitors 240 locations randomly dispersed throughout our system for Total Coliform Bacteria sampling 80 per month on a rotating schedule.

Total Coliform is the standard by which microbial contamination is measured.  Total Coliforms act as an indicator of possible contamination.  Non Coliform Growth (NCG) is often reported with water quality sampling and indicates that there were bacteria present but that it was not part of the Coliform group.  Additional testing may be required to determine the source of the NCG, but it poses no immediate health risks.

Pink Substance on Fixtures

It is very common to observe a pinkish colored substance forming around a drain, the water line of a toilet bowl, inside a washing machine or on the shower head in one’s home.  Due to the fact the substance is observed near a water outlet; many people believe the substance originates from the water itself. This is not the case.

The pink substance is a bio-film which is a compilation of microorganisms and bacteria which thrive in moist environments and are transported through the air.  The addition of food sources, such as phosphates from soaps, allows the bio-film to grow.  

The most effective means to prevent it from constantly reoccurring is to wash the area frequently and disinfect the surface using household bleach.  It is best to keep all surfaces as dry as possible, especially from standing water, in order to prevent the substance from reoccurring.   

Black "jelly like" Substance on Fixtures

Mount Pleasant Waterworks occasionally receives calls from customers expressing concern for the growth of a grey or black “jelly like” substance on faucets, showerheads, tubs or toilet bowls. Since the growth is always associated with water, many customers understandably assume the “jelly like” substance originates from the water supply.  However, the “jelly-like” substance does not stem from the water supply; instead, it is due to airborne fungal spores. 

The “jelly like” substance primarily forms and grows in moist areas.  For that reason, it is often observed on faucet aerators, washing machines, bathtubs, toilets, etc.  Warmer temperatures coupled with moisture exacerbates the problem; therefore, it is more common in the summer.

One of the reasons we are seeing the substance more often in recent years is due to new home construction standards, which limit the circulation of

outside air.  In other words, the air inside homes generally remains static preventing moisture around faucets and showerheads to completely dry.  In this environment, the fungal spores flourish.

Contact MPW:

If you have additional water quality concerns, please contact a Customer Service Specialist at 843.884.9626 or customerservice@mpwonline.com.

Learn More:

Water Disinfection

Chloramine Fact Sheet

Lead / Copper - Facts About Lead


Cryptosporidium / Giardia

Point-Of-Use (POU) Devices - Proper Maintenance of Home Water Treatment Devices

Safety Management and Risk Assessment Top Priorities for Mount Pleasant Waterworks