About Your Tapwater

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Frequently Asked Questions About Your Tap Water

What is the quality of our drinking water?
Mount Pleasant Waterworks meets all established limits for drinking water quality. Information about the constituents present in your tap water, and the levels of each of these constituents, is published in a WATER QUALITY REPORT that is mailed to all Waterworks customers annually. A copy of the report is available upon request from the MPW Operations Center, or can be accessed from our website at www.mountpleasantwaterworks.com.

Where does our drinking water come from? Mount Pleasant gets its water from two sources: Ground water and surface water. The ground water from deep wells in the Middendorf Aquifer is treated using reverse osmosis (RO). Supplemental treated surface water is purchased from Charleston Commissioners of Public Works (CPW). It passes through a meter located at the base of the Wando River Bridge.

More About our RO Treated Water . . .
The Middendorf Aquifer is between 1800 and 2500 feet deep and is confined between layers of limestone and sand. This means that nothing from the surface can contaminate it. The water is naturally clean, with little or no bacteria. There are dissolved salts, mostly chloride, fluoride, sodium and bicarbonates, which is why RO is the most effective treatment for us to use.

The finished water from our reverse osmosis (RO) water treatment plants is a blend of four parts of pure RO water with one part deep well, or source water. The process of reverse osmosis (RO) treatment efficiently and effectively removes dissolved minerals from our ground water supply.

Once treated, the water is 100% free of suspended matter and 90% free of dissolved salts, which means the water is very pure. However, very pure water cannot go directly into water system lines without treatment to raise the pH and make the water less aggressive to pipes and plumbing. MPW accomplishes this by blending back some of the deep well water with the pure RO water.

The water from our deep wells has naturally high pH and alkalinity, which reduces the aggressive nature of pure RO water. It also provides a beneficial amount of fluoride, one of the minerals found naturally in the Middendorf Aquifer.

Why does MPW have to buy water from CPW?
The Commission began purchasing drinking water from Charleston CPW in 1997. Up to one million gallons a day (MGD) at first ? then up to 7 MGD by the year 2015 ? will be blended with the 6.3 MGD of drinking water produced by our four RO water treatment plants. This allows us to get the maximum benefit from our current investment in RO and buy only as much extra water as we need to serve future growth.

How is CPW water different from the RO blended water from MPW's treatment plants?
The water from CPW is from a surface supply ? the Edisto River and/or the Bushy Park Reservoir. The treatment for surface water is very different from RO. This is because the constituents being removed from the water are suspended rather than dissolved in the water, and contain high amounts of organic matter. Although there is some degree of difference in pH, taste and odor, CPW's water meets the same high quality standards as MPW's.

Why is the cold water warm?
The temperature of MPW water as it comes out of the ground is very warm, about body temperature. Since it doesn't have a chance to cool down during the treatment process, it's still warm by the time it reaches your home. It may drop as low as 65 degrees in the winter but warms up to as high as 90 degrees in the summer months.

Why do we need to add a disinfectant to drinking water?
The SDWA requires public water systems to disinfect their water to eliminate and control specific disease-causing organisms and indicators that may be present in drinking water. Mount Pleasant Waterworks and Charleston Commissioners of Public Works use chloramine disinfection. Chloramines are formed by mixing chlorine and ammonia.

If you have an aquarium

Chlorine and ammonia are toxic to fresh water and salt water fish since water enters through the gill structure and goes directly in the bloodstream. Both chlorine and chloramines must be removed from aquarium water. However, chlorine dissipates quickly so it is easier to remove. Chloramines stay in the water for up to several weeks, so a dechloraminating agent must be added to remove it. The Commission provides chlorine/ chloramine-free water for aquariums at our reverse osmosis (RO) water dispensing stations.

Here's a checklist that will assure your aquatic pets stay healthy.

Are salt water fish affected by chloramines, too?
Yes. If the salt water aquarium contains chloraminated water, it must be removed.

Can I use a dechloraminating agent or filter system at home?
Pet suppy stores should have products which will quickly neutralize both the chlorine and ammonia molecules. The product label has instructions on the amount to use per volume of water to be treated.

How can you neutralize chloramine in a large outdoor pond?
Amquel can be used in large, outdoor ponds as well as in small, indoor aquariums. Sunlight and aeration will also de-chloraminate, but ask your pet supplier for the best method to use. Chloramine residuals in water used to keep fish should be kept below 0.1 part per million. Total-chlorine test kits are available from pet stores, pool supply stores and chemical supply houses.

FLUORIDE FAQs

What is the fluoride level in Mount Pleasant water?
The Commission maintains fluoride levels at between 0.5 and 1.2 mg/L - mg/L (milligrams per liter) = ppm (parts per million). Fluoride at these levels can help strengthen tooth enamel and prevent dental caries.

Isn't there a law that regulates fluoride levels in drinking water?
The SDWA has set the Maximum Contaminant Level for fluoride at 4.0 parts per million (ppm). This is a Primary (enforceable) Standard that water systems must meet. The Secondary MCL is 2.0 ppm, which is an aesthetic, rather than a health related standard.

FREE Reverse Osmosis (RO) Water

The Commission provides chlorine-free and chloramine-free water for customers at our Reverse Osmosis (RO) dispensing stations.The water at the dispensers is ozonated,not chlorinated. The service is free of charge. RO Dispensers are located in front of our three Reverse Osmosis (RO) water treatment plants: