Natatoriums are typically among the most corrosive environments facility staff must maintain. The design architect, HVAC engineer, and pool consultant must work together to reduce the causes of corrosion. In addition, all designers involved, along with facility personnel, need to be keenly aware of the factors that contribute to natatorium corrosion. The primary drivers of corrosion in natatoriums include:
Water Chemistry
The reaction between chlorine and biological material in the pool creates a group of organic compounds known as chloramines. These chloramines are released from the pool water into the air and are highly corrosive.
Condensation
Pool environments are typically maintained at approximately 80–85°F and between 50–60% relative humidity (RH) for occupant comfort. Any surface below the resulting dew point (typically between 60–65°F) can develop condensation. Combined with chloramines in the air, this moisture can corrode nearly every type of metal it contacts.
Proper pool chemistry can reduce chloramine levels, but chloramines will always be present to some degree. Splashing, spray, and condensation are also unavoidable in this wet environment. As a result, designers must implement measures to reduce corrosion risks, including:
Outdoor Air Ventilation
Exhausting chloramine-laden air and replacing it with fresh outdoor air helps dilute the concentration of corrosive compounds. However, increasing outdoor air ventilation also increases energy consumption and operating costs. Minimum ventilation rates should always comply with applicable codes and the recommendations of ASHRAE Standard 62.1.
Air Distribution
Proper HVAC air distribution should wash the building envelope and reduce stagnant areas where condensation can occur.
Material Selection
Even stainless steel can corrode in severe natatorium environments. Plain carbon steel should never be left unprotected. Epoxy-coated galvanized steel, aluminum, fiberglass, and treated 316-series stainless steel are all appropriate materials for pool environments. Surfaces should also be cleaned frequently using non-abrasive methods.
Dehumidification Capacity
Hundreds of pounds of water evaporate from the pool surface every hour. The actual evaporation rate depends on many factors and continuously varies. HVAC engineers must account for these conditions and properly size the dehumidification capacity of pool HVAC units to maintain the design relative humidity and space dew point.
The potential for corrosion will always exist in a natatorium. The key to successful design and operation of these facilities is recognizing the causes and minimizing the risk of corrosion.