Many school natatoriums are showing their age. Even those constructed with state-of-the-art materials 20 to 30 years ago are exhibiting the corrosive effects associated with the high humidity of pool environments. Heating, ventilation, humidity control, filtration, water treatment, plumbing and lighting systems have suffered from wear and tear. These systems may not meet health-department standards or satisfy campus needs.
Schools and universities use their pools for more activities than ever before. Community use has grown over the years, and special groups of users, including disabled persons, senior citizens and children in on-campus daycare facilities, also are getting into the swim.
Therefore, re-evaluating a pool program is important when planning a facility upgrade. It will help administrators identify the physical changes needed to accommodate new programs. The evaluation should consider the school's need to provide physical education; competition (including facilities for spectators and visiting teams); recreation; life-saving and water-safety instruction; synchronized swimming; water aerobics; sessions for disabled users; seniors; young children and other groups; and special activities.
The big three
Three critical engineering issues in older pools are recirculation, filtration and dehumidification. The pool recirculation system typically requires the greatest degree of modernization. Almost every applicable code requires that a pool be able to recirculate 100 percent of the pool's water through the main drains at the bottom of the pool and 100 percent from the top — that is, from the surrounding gutter. Unfortunately, many old pools take all the water for recirculation from the main drains and send the water that overflows into the gutter straight to the wastewater system.
New systems are designed so that under normal operation, 20 percent of the water to be recirculated is taken from the main drains and 80 percent from top, promoting a skimming action that helps keep pool water clean. Upgrading a pool to accomplish this usually requires a new gutter and a surge tank or balance tank to collect the overflow. If the budget does not allow for a new gutter, it may be possible to redirect overflow from the wastewater system to the surge tank or balance tank, but it will still be difficult to recirculate 100 percent of the water from the top, and a code variance will be required. Most codes also require water inlets to be adjustable both for direction and quantity, so these may have to be replaced.
Because of the corrosive action of chemically treated water, the recirculation system also is likely to need a piping retrofit — from cement-lined steel piping or ferrous material to CPVC plastic or PVC, depending on local codes. Pool volume dictates the capacity of recirculation pumps and the filtration rate.
That brings us to filtration. Most states require 100 percent water recirculation every six hours for recreation, competition and diving pools; a higher standard than what was typically in place 30 years ago. Standards are even higher for special circumstances. For a wading pool used by children under 6 — a possibility if there is an on-campus daycare program — the filtration system should produce a complete water change every two hours. Thus, schools must assess their pools' filtration rates to see if they need to be improved.
As for the filter itself, most older pools use diatomaceous earth filters, which are effective but require higher levels of maintenance. In some locations, they are treated as hazardous waste and require special disposal methods. As a result, many owners retrofit with high-rate sand filters if local regulations permit.
Once pool water is filtered, it is typically heated to 80 to 82°F. Water heaters often remain in working condition after 20 years, but pumps may require replacement. As for chemical disinfection, improved environmental standards require chemical tanks and piping to be double-walled to contain leaks. An emergency shower and eyewash also should be available in the pool equipment room.
It's the humidity
The corrosive effects of humid air often are the most visible problem in a natatorium. The ventilation system must be designed to provide adequate ventilation for three functions: user comfort, spectator comfort and humidity extraction.
Older systems typically were designed to introduce a percentage of dry, outside air to a natatorium under cool-weather conditions (up to 60° F), which mixes with the hot, humid air to provide user and spectator comfort, as well as a means of absorbing and exhausting moist indoor air. Above 60°, 100 percent outside air is drawn into the facility. These systems operate 24 hours a day to prevent humidity buildup. This type of ventilation system can be effective.
Today's trend is toward mechanical dehumidification and cooling to achieve uniform conditions year-round — or a combination of the two systems. It makes sense to analyze the costs and benefits of each situation. Most newer pools have pool covers to reduce evaporation and conserve energy.
Inadequate venting may lead to condensation in natatorium walls — in some regions of the country, ice forms and ruptures the walls. So, assess the conditions of walls and roofs to determine if the facility needs improved vapor barriers, insulation and venting.
Schools and universities also should assess their plumbing systems. For example, local health departments require that the pipes and valves bringing fresh water into a pool be designed to prevent backflow into the domestic water supply. Administrators also should evaluate flow-regulating valves, rate-of-flow indicators, drinking fountains, cuspidors and hose bibs.
Safety requirements for pools have become more stringent to protect users. For example, perimeter deck drains should be installed every 100 square feet to prevent slips and falls. A depth of at least 13 to 14 feet is required for diving, and diving boards are being removed in older pools that do not usually meet this standard. Starting blocks must be at the deep end of the pool.
Requirements for signage and depth markers also are more stringent. Schools and universities also should review their pool-supervision programs and record-keeping procedures to ensure they comply with codes.
Assess deck equipment — seating, storage, lifeguard stations, wall brackets and towel hooks — some of which may seem unimportant, but are necessary. Evaluate the pool vacuum pumps, grab rails, ladders, lap swim lane floats, float lines, backstroke flags, pace clocks, timing equipment, sports and recreation equipment and devices, instructional equipment and pool covers.
Make sure that the facility meets accessibility requirements — access to the building, locker and shower facilities, and hydraulic pool lifts.
At the college level, competition pools generally have been built to NCAA specifications, but schools still should check an existing pool's configuration to make sure it can support desired programs. A pool's design may rule out certain activities that require a uniform depth, although it may be possible to modify depth to meet new program needs.
Well-designed pool lighting enhances a facility's appearance and reduces maintenance costs. For these reasons, most lighting designers favor indirect lighting, which reflects light off the walls or ceiling to provide consistent overall illumination. Some owners also request underwater pool lighting.
Access doors and frames must be made of non-corrosive materials. Twenty years ago, treated standard steel often was used to cut costs, but this proved inadequate, and these materials have had to be replaced. The most cost-effective long-term solution is stainless steel. New ceiling materials, such as stretchable fabric, also are improving aesthetics while reducing maintenance. Ceramic tile still is favored for decking, walls and pool basins. It is available in more varied sizes and colors to allow greater design creativity.
Finally, a pool's security system should be upgraded to include emergency lighting, anti-intrusion devices and a water sensor that detects unauthorized swimmers. The pool director's office should have telephone, intercom and computer systems. And, of course, all electrical work must be grounded properly.
Number of critical engineering issues in older pools: recirculation, filtration and dehumidification.
Number of hours it should take for a pool system to recirculate 100 percent of its water.
Temperature at which most pools are typically heated.
Minimum depth (in feet) typically required in a pool to allow diving.
Sidebar: NYU upgrade does more than dehumidify
The recent renovation of the natatorium at the Jerome S. Coles Sports and Recreation Center at New York University shows that there often is more required than what initially meets the eye.
The Coles Sport Center was originally completed in 1981. Besides a natatorium, the 144,000-square-foot facility includes facilities for handball, basketball, volleyball, tennis, fencing and aerobics, plus a locker room and other support areas. The roof has a running track and tennis courts. For the most part, the original design has stood the test of time. But after nearly 20 years, the humidity had taken its toll on the ceiling and other architectural features.
In 1999, NYU decided to design a new dehumidification system to solve the corrosion problem. The school authorized a needs and condition assessment. Based on the evaluation, the project scope was expanded to install air conditioning, upgrade lighting and locker rooms, replace ceilings and other architectural elements, and install a new pool filtration system.
The new dehumidification system uses conditioned air to ensure a consistent year-round environment, replacing the center's original wall-hung unit ventilators, which used heated outside air and exhaust systems. The new dehumidification system required a mechanical room. The enclosure for the equipment could not go on the roof because of the running track and tennis courts. The solution was to insert it into existing natatorium space, extending it a full column bay into the building, and supporting it on the existing two-story columns.
One of NYU's significant concerns was maintenance. The pool's existing diatomaceous filter was replaced with a high-rate sand filter and the filtration system's ferrous piping replaced with CPVC piping.
A new vaulted ceiling was designed using a stretch ceiling membrane that is virtually maintenance free. Custom, wall-mounted indirect lighting replaced the overhead HID ceiling lights, resulting in more even distribution of diffused light as well as easier maintenance. The existing HID 100-watt metal halide lights were replaced with energy-conserving indirect 1,000-watt metal halide sources. The indirect design used the new curved ceiling material as a reflector, resulting in an even illumination for the entire ceiling.
Locker rooms and support spaces were renovated. The diving tank, at 15 feet, still meets safety requirements, so diving boards simply were replaced.
As a result of a well-planned renovation, the natatorium features new systems that will enable NYU to maintain a beautiful facility with less effort.
Ephron, AIA, is a partner and Bishop, PE, is an associate with Wank Adams Slavin Associates, an architectural and engineering firm in New York City. The firm designed the upgrades of the Coles Sports Center at New York University.