Cary has grown to the west and south where elevations are lower and water pressure is higher as a result. To stabilize pressure and to store adequate reserves, the Town has constructed two elevated water tanks and installed control valves to isolate pressure. Each new tank will supply a separate pressure zone, resulting in better control of water pressure.

Customers in the existing Central Pressure Zone will be unaffected. Most customers in the new Southern and Western zones will not notice any water pressure change inside their homes. This is because most home plumbing systems have valves that lower excessive water pressure.

Fall 2005 Update

The new water tanks have now been placed in service, creating the Southern and Western Pressure Zones. As with many new systems, the Town has had to make adjustments to achieve the desired level of performance. Both pressure zones are now at or near their normal operating conditions, but there may still continue to be minor adjustments.

The boundaries of the pressure zones were determined by including only areas where ground elevations were low enough to provide a minimum water pressure of 40 pounds per square inch (psi) under average demand conditions. The Town of Cary cannot guarantee a minimum water pressure, but requires that the water distribution system be designed to maintain certain minimum pressures under various demand conditions.

While the majority of water customers in these new pressure zones had to make no adjustments to their plumbing or irrigation systems, there are some systems that have required adjustments.

Plumbing systems
Some plumbing systems are equipped with a pressure reducing valve that throttles the flow passing through the valve so that the downstream pressure is reduced. This valve may need to be adjusted, and in some cases may be removed completely. (It is only required when system pressures are in excess of 80 psi.)

If your plumbing fixtures are "low-flow" or "water conserving," they may be causing excessive pressure losses. Adjusting or removing the pressure-reducing valve and changing fixtures has worked for some who have previously reported problems. Some water customers have made these modifications themselves, but others may need to consult a plumber.

Irrigation systems
Pressure losses are generated by water passing through the service line, meter, pressure reducing valve and backflow preventer. Depending on the system, these losses may be minimal and no adjustments will be needed. For other systems, these pressure losses will have to be reduced or eliminated for the irrigation system to function properly. Again, some irrigation customers have made these modifications themselves, but others may need to consult an irrigation contractor.

Southern Pressure Zone

Date of Implementation - April 5, 2005

Area Description - From the southern edge of Cary's water service area, the boundary runs northeast along US 1 to the intersection with Cary Parkway, then southeast along Cary Parkway to Tryon Road. It then extends northeast along a line between Tryon Road and Cary Parkway to Holly Springs Road. See a map.

Tank Location: 1010 Road at Plumtree Way, next to Cary Fire Station 6

Western Pressure Zone

Date of Implementation - October 18, 2005

Area Description - Generally west of Davis Drive and south of US 1&64. See a map.

Tank Location: N.C. 55 south of Morrisville-Carpenter Road

Household Effects

Residential plumbing systems typically have a valve regulating the pressure of water flowing into the home from the line in the street. Those pressure reducing valves should adjust automatically to the new pressure without customers having to check them. So people should not notice any difference in water pressure inside their home.

The water will not look, smell or taste any different because of the change in pressure.

Lawn watering may take a bit longer in the Southern and Western zones. Most automatic sprinklers work at full pressure, even if the home has a valve to reduce it. Washing machine tubs could fill less quickly in some homes, although most homes have the pressure reducing valves to keep pressure relatively constant.

Three customers in the Western pressure zone allowed the Town to install devices to monitor how plumbing systems would function at "reduced" pressures. The customers reported no differences in their plumbing systems during the testing in spring 2002. See test results.

Why Regulating Water Pressure is Important

Proper water line pressure ensures enough supply for customers and for fire fighting while protecting treated water from untreated groundwater.

A pressure zone is designed to keep water pressure within a range of 40 to 80 pounds per square inch. If the pressure is too low, so is the flow. If the pressure is too high, plumbing fixtures can leak and water bills will rise.

Generally, pressure will decrease approximately 20 pounds per square inch in the Town of Cary lines serving the new Southern Pressure Zone.

Fire Protection

Even with the new zones, water pressure will not be any lower than in the central part of Cary. Town officials have been planning the Western and Southern pressure zones since 1992 and have tried to keep people building in those areas informed.

A sprinkler system that was designed to handle the reduced pressure probably will not require any adjustment. A qualified engineer will need to check the sprinkler system to determine whether adjustments are necessary.

Water pressure is only one of several criteria that fire insurance rating services use. The change in system pressure should not affect homeowners' fire insurance premiums. Even with the new, lower pressures in the western and southern zones, the Town's distribution system will equal or exceed National Fire Protection standards.

The pressure change could affect commercial customers with calculated sprinkler systems. Individual engineering evaluations will be necessary for those sprinkler systems to determine whether equipment such as a booster pump is needed. The Cary Fire Department will work with these customers.

Contact

Glen Harrell, Project Engineer
Town of Cary Engineering Department
P.O. Box 8005
Cary, NC 27512
(919) 460-4933
glen.harrell@townofcary.org