The Town of Cary is committed to providing its citizens with the quality and quantity of water that they need. As the Town has grown to its west and south where ground elevations are lower, many customers in these areas experience excessive water pressure.

To stabilize the water pressure in the western and southern areas, as well as providing adequate reserve storage, the Town of Cary is constructing two elevated water tanks. The Plumtree Way tank is located on TenTen Road at Plumtree Way, next to new Fire station No. 6, and will establish the Southern Pressure Zone (SPZ). The Carpenter tank is located on NC Highway 55 just south of Carpenter-Morrisville Road, and will establish the Western Pressure Zone (WPZ).

Currently, the Town of Cary utilizes four water tanks, all located in a single water pressure zone, known as the Central Pressure Zone (CPZ). Each of the additional water tanks will create a new pressure zone, resulting in better control of water pressure.

WILL IT AFFECT ME?
Probably not - only customers that are in the newly created western and southern pressure zones as shown on the map will experience reduced pressures. And, they should not notice any pressure change since their current water service connection should already be provided with a pressure-reducing valve (PRV) to protect them from the current excessive pressures. Your actual pressure change at your water meter connection to the Town system will depend upon your ground elevation, size of local water mains and water system demand. For customers in the western pressure zone, the decrease will be about 40 pounds per square inch (psi). For those in the southern zone, the decrease will be about 20 psi. Your PRV should automatically adjust to the new reduced system pressure, with no action required on the customer's part.

HOW WILL I KNOW IF MY WATER PRESSURE DROPS OR RISES?
You would notice an appreciable change in the flow rate from house fixtures or plumbing. Minor changes in flow rate are normal and should not cause concern.

WHAT CAN HAPPEN IF MY WATER PRESSURE DROPS OR RISES TOO MUCH?
If the pressure drops too low, plumbing fixtures and appliances might not work efficiently. As the system pressure approaches zero, there is the risk of siphoning water from the plumbing fixtures that could contaminate the potable water system. If the pressure rises too high particularly above 80 psi, plumbing fixtures and appliances (primarily hot water heaters) could be damaged or leak excessively.

WHEN THE PRESSURE CHANGEOVER OCCURS, HOW LONG WILL IT TAKE?
Upon completion of the two new water storage tanks, town personnel will close certain valves within the distribution system to isolate the new pressure zone from the balance of the Town's distribution system. Once the last valve is closed, the changeover will occur over just a very few minutes. The entire process should be no more than a few hours.

DO I NEED TO BE HOME WHEN THE CHANGEOVER OCCURS?
No, you do not need to be at home when the changeover occurs.

WILL CHANGES IN THE WATER PRESSURE AFFECT MY BUILDING'S FIRE SPRINKLER SYSTEM?
That depends if your fire sprinkler system is designed to handle the reduced pressure. Town officials have been planning the Western and Southern pressures zones since 1992, and have made every effort to apprise new buildings of the pending change in system pressure. If your sprinkler system was designed for this change, then you should not need to adjust your sprinkler system. If not, then your system will likely require some modification. A qualified engineer will need to review the system design to determine the extent of any necessary adjustments.

WILL WATER PRESSURE CHANGES AFFECT THE FIRE DEPARTMENT'S ABILITY TO FIGHT FIRES?
No. Water pressures and available volume of water for fire flows will be adequate throughout the system after the pressure zone implementation. After this project, pressures nowhere in the system will be lower than they already are in the unaffected portions of Town.

WHAT SAFETY MEASURES ARE IN PLACE TO ENSURE FIRE PROTECTION?
The Town's Water System Master Plan, completed in March 2000, includes a computer model of the Town's water distribution system. This model simulates the water flow during periods of normal operation and peak demand; such as required to provide fire protection. Engineers used this model to confirm that the Town's water distribution system will be capable of meeting all domestic and emergency water needs. This model was calibrated and verified with extensive field testing of the existing water distribution system. In addition, Town Fire Department and Utility personnel regularly perform maintenance and conduct field tests in the distribution system to confirm peak flow performance. The Cary Fire Department performs regular risk assessments, including fire flow tests, throughout their service area to ensure adequate availability of water for fire flow.

WILL THE CHANGES IN CARY'S PRESSURE ZONES AFFECT MY FIRE INSURANCE PREMIUM?
Water pressure is only one of several criteria used by insurance rating services. Residential customers should not be impacted by the change in system pressure. Even with the new lower pressures, the delivery pressure and water volume available from the Town's distribution system will equal or exceed National Fire Protection standards.

There may be, however, some affect on commercial customers with calculated sprinkler systems. These customers will need to perform individual engineering evaluations to determine whether they will need to add supplemental equipment such as booster pumps. Their insurance premiums would only be affected if they failed to make recommended improvements. The Cary Fire Department will work with these customers on a case-by-case basis.

HOW WILL CHANGES IN THE WATER PRESSURE AFFECT MY AUTOMATIC IRRIGATION SYSTEM?
Most automatic sprinkler systems utilize the current full system pressure even if your house or building has a PRV. With the lower water pressure in the new pressure zones you might need to adjust your watering duration and frequency to maintain the same level of performance.

Some irrigation systems within the Southern and Western Pressure Zones may need adjustments in order to operate effectively. Listed below are four ways to enhance your irrigation system's performance due to low pressure. These suggestions may not be appropriate for all situations, so consult an irrigation contractor/specialist for recommendations on your best option. Contact Rick Jordan, water conservation technician, at (919) 462-3879 or rick.jordan@townofcary.org if you have specific questions about the four options. Contact Glen Harrell of the Town's Engineering Department if you have questions about the new pressure zones.

1. If your system has a pressure reducing valve, adjust it to compensate for the lower pressure.
2. Replace nozzles with ones that have lower gallon per minute requirements.
3. Divide larger zones in half.
4. Install a booster pump after the backflow preventor.

Policy Statement on Minimum Water Supply Pressure

WHY DID THE TOWN INSPECTOR PASS MY (PLUMBING/IRRIGATION) SYSTEM IF THE TOWN WAS GOING TO REDUCE THE PRESSURE?
The purpose of the Town of Cary inspections is to ensure compliance with applicable codes and ensure the safety of the public water system. While the Town inspectors may point out potential performance issues, they do not ensure the performance of any private system. The performance of any private system is the responsibility of the designer and owner of that system.

HOW DO YOU ADJUST A RESIDENTIAL PRESSURE REGULATING VALVE (PRV)?
There are many models of PRV's, and the Town recommends that the plumbing system owner consult the manufacturer for specific instructions. Two typical models are Wilkins and Watts.

Get more Information on the Wilkins model or the Watts model.

WHERE IS MY PRV LOCATED?
PRV's are typically located in the crawl space or basement on the main service line from the meter and near the main shut-off valve. In some cases the PRV is located near the main shut off valve in a mechanical room or closet.

See an example of a PRV.

DOES MY RESIDENTIAL PRV REQUIRE MAINTENANCE? HOW CAN I TELL IF IT IS DEFECTIVE OR NEEDS ADJUSTING?
The Wilkins Web site referenced above includes the following statement: "Annual inspection and maintenance is required of all plumbing system components. To ensure proper performance and maximum life, this product must be subject to regular inspection, testing and cleaning". This same site has a TROUBLESHOOTING section that describes typical problems with PRV's.

CAN THE HOMEOWNER ADJUST OR REMOVE A PRV, OR DOES THAT REQUIRE A PLUMBER? WHAT DOES A PLUMBER CHARGE TO REMOVE OR ADJUST A PRV?
Adjustment or removal of a residential PRV may be performed by the property owner or a licensed plumber. Two area plumbers advised Town staff that the charge to adjust or remove a residential PRV would be around $100 to $150.

THE WILKINS WEB SITE TROUBLESHOOTING SECTION INDICATES THAT UNSTEADY OR VARIABLE PRESSURE AND FLOW MAY BE CAUSED BY WATER DEPARTMENT MAINS BEING INADEQUATE FOR THE DEMANDS PLACED ON THEM. WHY IS THAT NOT THE CASE WITH THE NEW PRESSURE ZONE ISSUES?
Some municipalities may have water distribution systems that are not designed for fire protection. In those systems, the mains may be small enough to create high pressure losses as the water passes through the mains at high velocities. The Town water system is designed to provide fire protection and the mains are sized to maintain a certain minimum pressure in cases of very high flows of water that may be required to fight fires. The much smaller flows normally experiences due to even high demand periods of domestic or irrigation usage will create very little pressure losses.

HOW WILL CHANGES IN THE WATER PRESSURE AFFECT MY BUILDING'S COOLING SYSTEM?
No change is anticipated to building cooling systems.

MY BUILDING STILL HAS RADIATORS. HOW WILL THE CHANGE OVER AFFECT THAT SYSTEM?
The change will not affect your radiator system, since such systems are not directly connected to the water distribution system. Steam heat is not dependent upon water pressure. A boiler that maintains a set volume of water provides steam heat.

HOW WILL CHANGES IN THE WATER PRESSURE AFFECT MY WASHING MACHINE?
The water service connection for most residential customers should be equipped with a PRV. This type of valve automatically adjusts to changes in system pressure to maintain a relatively constant pressure in your home's plumbing fixtures. If the supply pressure to your washing machine does decrease significantly, you may notice an increase in the fill time per cycle. Such changes, if they occur, should not cause any significant problems.

HOW WILL CHANGES IN THE WATER PRESSURE AFFECT MY AUTOMATIC ICEMAKER?
The water service connection for most residential and commercial customers in the new service zones should be equipped with a PRV. This type of valve automatically adjusts to changes in system pressure to maintain a relatively constant pressure in your plumbing fixtures. If the supply pressure to your icemaker does decrease, then you may notice some increase in the fill time for each cycle. Such changes are not expected to be significant.

HOW WILL CHANGES IN THE WATER PRESSURE AFFECT MY SWIMMING POOL, HOT TUB?
Swimming pools and hot tubs are not directly connected to town's water system. They will not be affected by the pressure change.

WILL THE WATER TASTE, SMELL, OR LOOK ANY DIFFERENT IN DIFFERENT PRESSURE ZONES?
The new pressure zones will not change the taste, smell or look of water from the Town's distribution system.

WILL THE STREETS AND SIDEWALKS BE TORN UP AS THE NEW PRESSURE ZONES ARE DEVELOPED?
The only noticeable construction will be the two new elevated tanks and several valves that are being installed at key locations in the distribution system. No other construction is required to create the new zones. Most of the valves required to separate the pressure zones are already in place.

UNDERSTANDING WATER PRESSURE:

WHY DO WE NEED WATER PRESSURE?
Water pressure provides the energy needed to deliver water to you. Maintaining a positive water pressure also serves to protect the water quality by protecting it from untreated groundwater with which the pipelines might come in contact.

HOW DOES THE TOWN ACHIEVE WATER PRESSURE?
Pumps located at the water treatment plant and elsewhere in the distribution system maintain the water pressure. These pumps are controlled to maintain the water level in the various elevated tanks located throughout the distribution system.

WHAT TYPE OF MEASUREMENT IS USED TO REPORT WATER PRESSURE?
Water pressure is normally reported in pounds per square inch (psi) and is measured with a gauge installed on the piping system.

WHAT IS CONSIDERED NORMAL WATER PRESSURE?
The typical water pressure for a municipal distribution system is between 40 - 80 psi, and should always be above 20 psi. If the system pressure exceeds 80 psi, the State plumbing code requires a PRV, which is normally set to maintain pressure at 60-65 psi.

WHAT IS A PRESSURE ZONE?
Water pressure such as Cary's is controlled by the height of one or more elevated water tanks. The overflow elevation for the tank(s) determines the maximum normal operating pressure for the area served by that tank. Each area served by a tank at the same overflow elevation is commonly referred to as a "pressure zone."

WHAT IS THE PURPOSE OF A PRESSURE ZONE?
Pressure zones are intended to maintain water pressure within the typical range of 40-80 psi. If the pressure were too low, then the delivery volume would be too low to meet domestic and emergency needs such as fire flow demands. If the pressure is too high, then it can damage standard plumbing fixtures and cause excessive leakage. Pressures above the normal range can also provide a significant energy cost.

WHAT DETERMINES WHEN A PRESSURE ZONE IS NEEDED?
Mainly topography. Maximum water pressure occurs during periods of minimum demand, which is usually at night. During these low flow conditions, the water system pressure approaches its maximum, which is controlled by the tank overflow elevation. If your ground elevation were significantly lower than the tank overflow elevation, then you would have unacceptable high pressures. Likewise, if you are in higher ground elevations that begin to approach the overflow elevation, your system pressure would decline to the point of being unacceptable.

WHY DO WE NEED MORE PRESSURE ZONES NOW?
The water service areas west and south of Town have much lower ground elevations than the central areas of Town. These areas need the new pressure zones to reduce the excessively high normal operating pressures. A study of water pressures and topography revealed well-defined pressure zone boundaries generally along Davis Drive in the west and US 1-64 in the south. A more detailed diagram and map are available.

WHAT DETERMINES WHERE A PRESSURE ZONE WILL BE?
The pressure zone boundaries are determined by a study of the prevailing ground elevations, system demands, and the layout and sizing of the pipeline. The zone boundaries are selected to maintain water pressures in the typical range of 40-80 psi as well as to adequately respond to periods of peak demand.

HOW MANY PRESSURE ZONES DOES CARY CURRENTLY HAVE?
The Town's current distribution operates on a single pressure zone with an overflow elevation of 641 feet. Operation on a single pressure zone is typical for smaller systems where the range of ground elevations within the distribution system does not vary by more than about 100 feet. The Town of Cary is currently providing water to customers with ground elevations ranging from about 530 to 280 feet above sea level, or a range of 250 feet.

HOW MANY PRESSURE ZONES WILL CARY ULTIMATELY HAVE?
The master water plan for the Town currently provides for a total of three pressure zones. The central portions of the distribution system will remain in the historical pressure zone that will be referred to as the Central Pressure zone with an overflow elevation of 641 feet. Areas west of town including the Research Triangle Park areas will be in a new pressure zone known as the Western Pressure zone with an overflow elevation of 540 feet. Areas generally located to the south of town will be in a new pressure zone known as the Southern Pressure zone with and overflow elevation of 595 feet. Additionally, a fourth pressure zone will be located in the vicinity of RDU International Airport in the near future. This Airport Pressure Zone (APZ) will operate on an overflow elevation of 540 feet. More information will be provided on this separate project at a later date.

WILL THE WATER PRESSURES BE DIFFERENT AMONG THE DIFFERENT PRESSURE ZONES? IF SO, HOW DIFFERENT?
No, creation of the new pressure zones will make the water pressure in all portions of the Town's system more uniform. Current areas of excessive high pressure will be eliminated by lowering the water pressure in those areas back to the range that has been experienced in other sections of the distribution system.

WILL THE NEW PRESSURE ZONES AFFECT PEOPLE IN APEX AND MORRISVILLE WHO GET WATER THROUGH THE CARY-APEX SYSTEM?
This change will not impact the Apex and Morrisville water systems.

FOR THOSE CUSTOMERS IN THE AREAS TO BE REDUCED, WHAT ARE THE EXCESSIVE PRESSURES THAT MOST CURRENTLY EXPERIENCE?
In the western area, pressures are typically in excess of 110 psi, and frequently exceed 125 to 140 psi. In the southern area, pressures are typically in excess of 90 psi, with highest pressures of 120 to 130 psi. Compare this to pressures in the Central Pressure Zone, which typically range from 65 to 90 psi, with occasional isolated pressures in excess of 100 psi.

HOW MANY WATER CUSTOMERS DOES CARY HAVE?
HOW MANY WATER CUSTOMERS WILL BE AFFECTED BY THIS PROJECT?
Cary has over 31,400 water customers. Nearly 22,400 of these customers are in the Central Pressure Zone and will not be affected by this project. 4,400 customers will be affected by the Southern Pressure Zone and nearly 4,600 will be affected by the Western Pressure Zone. 74 customers are located in the area designated for the future Airport Pressure Zone.

HOW MANY PRESSURE ZONES DO RALEIGH AND APEX HAVE?
Raleigh currently operates with four pressure zones ranging in elevation from 495 to 655 feet. The Town of Apex currently operates at a single pressure zone with an overflow elevation of 617 feet. Long range planning for the Town of Apex indicates that they will also need a new "western pressure zone" as their growth moves in the direction of Jordan Lake where the ground elevations are much lower.

ARE THERE ALTERNATIVES TO CREATING PRESSURE ZONES?
There really isn't an alternative solution that provides both a comparable uniform system pressure and maintains the reliability of the Town's existing distribution system. The tank-fed system allows the distribution system to automatically respond to peak demands and system emergencies. The creation of new pressure zones is the typical and standard response for all public water systems faced with the similar problem. Elevated water tanks are by far the most economical means of providing system storage reserves, and should be located throughout the service area rather than centralized in one area to provide maximum benefit. Extremely tall tanks would be required in the west and south if the pressure zones were not reduced, with heights over 250 feet. None of the major tank manufacturers surveyed have built tanks this tall.

WHO DECIDED THAT CARY NEEDS NEW WATER PRESSURE ZONES? WHEN?
Engineers working for the Town first recommended the creation of the new zones in a 1992 Water Master Plan prepared for the Town. In March 2000, the Town completed an updated water system master plan that reconfirmed the need for the new pressure zones and made minor adjustments in the boundary limits. There is now a sufficient number of water customers in the affected areas to justify construction of the elevated water tanks that will establish the new pressure zones.

WAS THERE/WILL THERE BE ANY CITIZEN INPUT INTO THE WATER PRESSURE ZONE DESIGNATIONS?
No. This is a purely technical engineering issue for which the Town has mobilized some of the most qualified and highly respected professionals in the field.

WHO IS WORKING ON THE WATER PRESSURE ZONE PROJECTS WITH CARY?
Town engineering staff and engineering consultants has been involved in establishing the need for the pressure zones. Camp Dresser and McKee completed the Water System Master Plan and computerized model in March 2000, which finalized the pressure zone boundaries and established a timetable for implementation. Hazen and Sawyer designed the two new water tanks and pressure zone implementation plans.

HOW MUCH IS ALL THIS COSTING?
Final estimates being completed and will be posted as soon as they are completed.

HOW IS IT BEING PAID FOR?
The Plumtree Way and Carpenter elevated water storage tanks and are being funded with the Water System Bonds approved by voters in February 1999.

HOW CAN I GET MORE INFORMATION ABOUT THESE TOPICS?
The Town of Cary is committed to informing its citizens regarding the pressure changes. It is mailing brochures to all residents and business owners in the affected areas, providing updated information on its web site, www.townofcary.org, and providing tip sheets at hardware stores and libraries. You may also contact the Project Engineer, Glen Harrell, PE, PLS, at 919-460-4933 (glen.harrell@townofcary.org) with more specific questions.