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Water Utilities  |  620 Small Hill St.  |  P.O. Box 534045  |  Grand Prairie, TX 75053
Phone  972-237-8413 or 237-8400  |  Fax  972-237-8412  |  E-mail
Why Does the Water Taste Different?
Why is the water running?
Why are there flags and paint in my yard?
Q: Why Does the Water Taste Different?
  1. As the seasons change, water supplies undergo natural processes that impact the taste and odor of drinking water. These changes, while some times a nuisance, do not indicate unsafe drinking water. Grand Prairie water is tested daily to ensure that it meets all state and federal regulations, which are based on human health research. If these standards are not met, we are required to notify you.
  2. The seasons that typically have the greatest impact on the taste and odor of our drinking water are spring and summer. Heavy spring rainfall, higher temperatures and more sunlight accelerate the growth of algae in the water. Algae are microscopic plants, which grow in rivers and lakes.
  3. In the spring, heavy rains bring organic matter (sediment) into the watershed, sometimes leading to “earthy” or “musty” tastes. This matter acts as a “fertilizer” to the algae, encouraging its growth, especially during long periods of sunlight.
  4. Most episodes of taste and odor cannot be removed by conventional treatment processes. The algae “bloom” must run its course before the taste and odor subside.
  5. In the summer, the city supplements its purchase of surface water with water wells. The mix of these different supplies is noticeable to those who have become used to surface supplies during the course of the year. Our ground water meets the same standards as our surface water, but tastes different.
  6. Ground water naturally contains a high dissolved mineral content, which will give it a more distinct taste. The presence of natural minerals gives water much of its taste. Water without minerals (distilled) tastes flat.
  7. Sometimes people detect the odor of chlorine in their water. This is a disinfectant used to ensure the biological integrity of the water and is mandated for use by the federal government. Usually the odor will be most apparent after first turning on the water. After a few minutes, the odor usually fades. Before the use of chlorine, waterborne diseases were a major problem. Its use has virtually eliminated diseases such as typhoid, cholera and dysentery.
  8. “Milky” water is often caused by the presence of tiny air bubbles. To confirm this, pour some water in a glass. If the water starts to clean immediately from the bottom up, the cause was entrapped air bubbles.
  9. Cooling water in your refrigerator in an open container will improve the taste and odor of your water.
  10. Speakers on water conservation are available to talk to civic groups, community and charitable organizations. For more information, call 972-237- 8377 or e-mail 

Q: Why is the water running?

flush Have you ever seen a city of Grand Prairie truck sitting in  front of a fire hydrant that was wide open allowing water to flow down the street? When you passed that truck, did you ask yourself “Why are they wasting water?”

Well, there are many reasons why we are flushing these hydrants and all of them have to do with protecting public health.

Background Information

The City of Grand Prairie purchases its water from the cities of Dallas and Fort Worth (about 90% from Dallas and 10% from Fort Worth). The treated water from these cities enters Grand Prairie at 3 locations and is pumped through 700+ miles of pipe to service residential and commercial needs. This water is treated with a chemical compound called Chloramine (a combination of Chlorine and Ammonia). Chloramine is the active disinfectant used to prevent bacterial growth in our water system. Over time, the level of chloramines in the system may dissipate due to: age, temperature or demand.

Regulatory Requirements

The minimum disinfectant (chloramine) residual for our system is 0.5 mg/L. Studies show that this is the lowest level that chloramines can effectively prevent bacterial growth. The state’s rules also require us to keep enough water in storage to provide adequate pressure for use and fire fighting activities. Finally, the City is required to periodically flush “dead ends.”

So, why is the water running???

Why is the Water Running When you see a fire hydrant flowing water, it is typically for one of the reasons listed below. To find out more about each, click on the topic that interests you.

Dead End Flushing

Dead End signAll cities in the state of Texas are required to flush areas of their water system called Dead Ends. Dead Ends in the water system are like dead ends on the street; they are points of no return. They often occur where streets terminate. So, why do we have to flush these areas? As water ages, the level of chlorine residual decreases and the chance of bacterial growth increases. When water gets to a dead end, it stays there until it is used, which may be several days depending on the size of the water line and the usage. So, to keep fresh water flowing in these dead in areas, the City will open a fire hydrant or install a pipe known as an automatic flush site. Water in these areas is flushed at least once a month to maintain disinfectant residual and palatable water.


New Construction

In 2007, the City of Grand Prairie was rated as the 5th fasted growing city in the nation! With that growth comes a need for new and more water lines. Before these new lines are put into service, they must be disinfected by adding a high concentration of chlorine. New water lines are required to be disinfected with 50 mg/L of chlorine solution. The maximum amount of chlorine (or chloramine) that can be delivered to customers is 5 mg/L. Since the disinfection dosage is so high, that water in the pipe must be “dumped” and replaced with potable water, i.e. water with less disinfectant. The “super-chlorinated” water to be dumped is first de-chlorinated then released to the streets and storm drainage system.



Super-Chlorinating Just as you have to clean your car or bath tub, the water system has to be occasionally cleaned. This cleaning is accomplished by adding high doses of chlorine to the pipes, a process called Super-chlorination. Super-chlorinated water cannot be consumed by the public, so it must be “dumped.” To ensure that no one consumes super-chlorinated water, the water meters along the section of pipe being treated are disconnected. After allowing the high chlorine dose to do its work, usually overnight, a fire hydrant is opened to release the non-potable water.


Water Quality

Occasionally, citizens will contact city offices with concerns about the taste, odor or appearance of their drinking water. We classify these concerns as Cartoon character drinking waterwater quality complaints. In addition to checking our water system and collecting analytical samples, city crews will often open fire hydrants to “dump” water of poor quality and “pull” water of favorable quality to the area of concern. How does the water become “poor”? Several factors can contribute to water tasting different. Some of the most common factors are low usage, temperature, and changes in source water. Low water usage can lead to “old” water which may develop unpalatable tastes. Coupled with low water usage, temperature can affect the taste and odor of water by causing pH fluctuations. As the pH changes, the active disinfectant changes its configuration and develops an odor. Although this change does not pose any health threats, it does make the water difficult to drink. This problem is easily solved by opening a fire hydrant to release the old, warm water and draw fresher water to the area of concern.


Unidirectional Flushing ProgramUnidirectional Flushing Program

The Unidirectional Flushing Program, also known as UDF Program, is a method of cleaning the water mainlines through a network of flushing sequences with the water being discharged from a fire hydrant. A UDF program involves closing valves in a specific sequence to create water movement in one direction while opening specific hydrants at the end of that sequence. Maintaining the flushing sequence is important so that the water used in the flushing sequence remains clean. The UDF technique allows higher water flow velocities by isolating certain sections of water mains. This higher water velocity allows for better scouring of pipes. The flushing of the pipes will dislodge and remove mineral deposits, sediments and biological deposits that accumulate in the water mains.


Servicing Groundwater Wells

Q: Why are there flags and paint in my yard?

line locatesIf you have ever experienced an extended loss of utility service — gas, electric, telephone, sewer or water, due to accidental damage, you will understand the importance of these paint markings, paint and flags that service providers use to mark out their underground pipes and wires. Mark-outs can be a minor inconvenience. Painted codes can be a little unsightly; paint and flags can get in the way. The alternative, however, can be very serious. Excavation work performed without clear mark-outs can damage underground facilities. Loss of certain utility services drastically affects your way of life. Accidents can be very dangerous.

What's the solution? Simple patience. Dig Tess One Call is a service established by law to provide the highest possible assurance that excavations will not disrupt utility services. To be in compliance with the law, contractors must obtain mark-outs, and once they have been established, excavation must commence within 10 business days. After that the flags may be removed. Considering the potential problems, you will understand that mark-outs must be clearly visible. And while we understand that such visible markings can be a bit unsightly, it's important that anyone whose property is marked cooperate with the procedure. The paint that isn't eventually removed by the actual excavation will wear away faster than you'd imagine, or will grow out on a lawn and disappear with mowing.

It's very important that you avoid moving or removing flags or stakes if at all possible. 

American Public Works Association Uniform Color Code


Electric power lines, cables or conduits, and lighting cables.


Gas, oil, steam, petroleum or other hazardous liquid or gaseous materials.


Communications, cable TV, alarm or signal lines, cables or conduits.


Water, irrigation and slurry lines.


Sewers, storm sewer facilities, or other drain lines.


Proposed excavation.


Temporary survey markings.


Reclaimed water, irrigation and slurry lines.

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