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Swimming and Spa Pools

An article by Catherine Houska, Technical Marketing Resources, Consultants to IMOA

Stainless Steel Swimming Pools, Therapy Tubs & Spas

Whether the application is interior or exterior, stainless steel is the ideal material for a wide range of swimming, spa and therapy pool facility applications. Stainless steel is used in pool liners, ladders, railings, diving platforms, lockers, doors, ventilation systems, lighting, and other applications. The key to success is selection of an appropriate stainless steel and finish for each application, adequate maintenance, pool water chemistry control, and regular air replacement in the pool building.

Why Use Stainless?

Stainless steel is a popular choice for pool areas because of its long life, low maintenance costs, design flexibility, and hygienic benefits. Its ease of bacteria, virus, and algae removal is comparable to glass, making it the hygienic choice for pool applications, therapy facilities, and other applications where cleanability is critical.

Seismic performance is an additional important benefit. Stainless steel swimming pool liners have withstood earthquake damage under conditions where traditional concrete and fiber-reinforced polymer (FRP) pool linings have failed.

The hot tub and integral stainless steel waterfall and fountains show the design flexibility of welded stainless construction.

 Design Advantages

While most people are familiar with the classic applications for stainless steel, many popular new design concepts are naturally suited to this flexible material. These include integral fountains, infinity edges, and other creative elements. Vacation venues and theme parks use stainless steel liners for water rides, elaborate pools, and even endlessly flowing rivers with currents that carry bathers along their curving paths.  

Stainless steel’s design flexibility makes possible creative designs like this Type 316 continuously flowing beachside river.

Stainless steel pool liner and structural support systems are designed in advance and can be installed more rapidly than traditional systems. This is advantageous when relining commercial and public pools, and for new construction projects when it is desirable to limit construction disruption and pool closure time.

Advance design and prefabrication of components can speed installation of stainless steel pools and spas.

A variety of stainless steel finish options is available. Bare stainless steel is often used with a mirror polished or brushed directional polished finish. These popular finishes are used for applications ranging from handrails to pool liners. The smoothest finishes provide better corrosion resistance and are more easily cleaned. Rough abrasive blasted and coarse polished finishes are not advised because they are susceptible to hard-water staining and corrosion.

Pools, hot tubs, and spas are sometimes lined with custom tile designs or weldable PVC coatings. Decorative ceramic tile may be applied on part or all of a welded stainless steel liner. PVC clad stainless steel pool liners are assembled with mechanical fasteners, after which the PVC is fused at the seams.

Spa & Therapy Pools

Therapy pools were one of the early applications for stainless steel liners because of their hygienic requirements, but stainless has also become popular for the growing number of spa and hot tub pools found in private residences, resorts, and public facilities.

Spa, therapy and hot tub designs for commercial and private installations are limited only by the imagination.

The higher temperatures used in these pools can increase bacteria and virus levels. Higher chlorination levels are typically used to disinfect them, making these application environments more corrosive than that of the typical recreational pool. Stainless steels are a logical choice, but Type 316 or a more corrosion resistant molybdenum-containing grade should be selected.



Appropriate stainless steel specification depends on the water sanitation method (e.g. chlorination or bromination) and concentration, water temperature, and the type of application. Particular care is needed when selecting steel for load-bearing structural applications near ceiling level, and for elevated-temperature pools with high chlorination levels.

For exterior water features, pools, and fountains, designers should consider the effects of evaporation on chlorine concentration. This is particularly true in hot, arid environments. When these conditions exist, automatic or regular manual monitoring is suggested so that water chemistry can be adjusted to avoid excessively high chloride levels. Care should also be taken in areas where potable water is naturally high in chlorides.

Water treatment to reduce mineral content should be considered when there are high levels of dissolved solids (hard water), because evaporation of splashed water may result in mineral stains. These can be removed, but this increases maintenance costs. Excess iron in the pool water supply should always be removed to prevent staining.

A Type 316 liner was selected for this California residential lap pool because it is on the beach, where chlorides from the ocean create a more aggressive environment. The molybdenum in Type 316 renders the steel resistant to the seaside environment

The articles and references found in this section of the website cover many of these topics in detail.

Successful Stainless Swimming Pool Design provides specification advice for the broadest range of applications.
Molybdenum Brings Safety into Swimming Pool Buildings addresses load-bearing ceiling applications.
Thanks to Molybdenum Stainless Steel, Swimming Pools Last “Forever” reviews case studies of European swimming pool relining experience.

Photo Credits – all photos: Bradford Products