A stainless steel pool shell is manufactured in a controlled shop, not formed on site. Designers produce shop drawings, fabricators cut and form stainless steel plate, then weld it into wall sections or a complete vessel. The shell is cleaned, pressure and static tested, and shipped whole or in sections for assembly and final testing on site.
This guide walks through each stage for architects, aquatic designers, and facility owners who are specifying a commercial stainless steel pool. It also covers the grade decision that matters most for long-term corrosion performance, and the questions worth asking any manufacturer before you commit.
What Is a Stainless Steel Pool Shell?
A stainless steel pool shell is the welded metal structure that contains the pool water and gives the pool its shape. Depending on the system, it can be a complete self-contained vessel or a stainless steel wall system that works with a separate floor and interior finish.
Commercial systems generally fall into two groups:
- Complete vessels. Common for elevated pools, rooftop pools, spas, and cold plunges. The walls and floor are fabricated as one welded unit or as sections welded together on site.
- Wall systems. Common for in-ground commercial pools. Welded stainless steel wall panels, supports, and often an integrated gutter form the pool perimeter.
RenoSys manufactures both. Its commercial stainless steel pools are all-welded 304L or 316L stainless steel, built for in-ground public pools. Its SummitSeries vessels are designed for elevated pools and spas.
How Is a Stainless Steel Pool Shell Manufactured, Step by Step?
The exact sequence varies by manufacturer and by project, but most commercial stainless steel pool shells move through these stages:
- Design and shop drawings. The pool geometry, depths, penetrations, supports, and gutter are detailed for fabrication.
- Grade selection. The stainless steel grade is chosen based on water chemistry, chloride levels, and indoor or outdoor exposure.
- Cutting and forming. Plate is cut to size and formed into wall, floor, step, and corner components.
- Welding. Components are welded into wall sections, corner assemblies, or a complete vessel.
- Weld finishing and cleaning. Welds are finished and surfaces are cleaned to restore corrosion resistance.
- Testing. The shell is tested for watertight integrity before it is released.
- Shipping. Smaller vessels ship whole. Larger pools ship in sections sized for transport and site access.
- Installation and field testing. Sections are set and welded together on site, then tested again once assembled.
- Interior finish. The pool receives its final surface, such as natural stainless steel, tile, or a PVC membrane.
The sections below explain what happens at each stage and what a specifier should look for.
Stage 1: Design and Shop Drawings
Every commercial stainless steel pool starts as a set of fabrication drawings. These translate the architect’s or aquatic designer’s intent into exact dimensions for every panel, weld, support, and penetration.
Shop drawings typically resolve:
- Pool footprint, depth profile, steps, benches, and any vanishing edge
- Locations of main drains, inlets, lights, and other wall or floor penetrations
- Wall support and bracing design
- Gutter type and how it integrates with the pool wall
- How the shell will be divided into shipping sections, if needed
Penetrations deserve extra attention. Locating them in the shop means fittings can be welded in during fabrication, rather than cut into a finished shell in the field. RenoSys designs its stainless steel pools with no exposed compression fittings and uses patented stainless steel wall buttresses for support. Its in-house CAD designers prepare project drawings and can work with the project’s architect or engineer.
The shop drawings also connect to the rest of the building. On an elevated pool, the building’s structural engineer of record designs the structure that carries the shell. On an in-ground pool, the general contractor prepares the excavation and site. The pool manufacturer’s drawings need to match both.
Stage 2: Choosing the Stainless Steel Grade
Grade selection is the single most important material decision in a stainless steel pool. The two grades used for most commercial pool shells are 304L and 316L. The main difference is molybdenum, which improves resistance to chloride pitting and crevice corrosion.
The “L” in each grade means low carbon. According to technical data from Langley Alloys, 316L is limited to 0.03% carbon, compared with 0.08% for standard 316. That lower carbon reduces the risk of sensitization and intergranular corrosion in the heat-affected zone around welds. For a fully welded pool, that matters.
| Property | 304L | 316L |
|---|---|---|
| Molybdenum | None | 2–3% |
| Carbon | Low-carbon “L” grade | Low-carbon “L” grade (0.03% max) |
| Maximum recommended pool water chloride level | 250 ppm | Up to 500 ppm |
| Relative chloride pitting resistance | Good | Higher |
Sources: chloride limits from the International Molybdenum Association; composition from Langley Alloys technical data.
Why chloride levels drive the grade decision
The International Molybdenum Association advises that 304L should not be exposed to chloride levels above 250 ppm, while 316L used for the lining, gutters, and water handling system can tolerate up to 500 ppm. It notes that some municipal potable water supplies already approach 500 ppm, so source water chloride data should be collected during design.
Chloride levels can climb over time in pools that lose a lot of water to evaporation, pools in arid or coastal regions, and pools where chloride-containing chemicals are added. Water chemistry maintenance is part of protecting the shell.
What about saltwater pools?
Saltwater pools need a different conversation. The International Molybdenum Association states that common grades like 304L and 316L should not be used for saltwater pool linings, ladders, or water handling equipment. Higher-alloy stainless steels can withstand those conditions, but they cost more and require specialized fabrication.
If a saltwater system is planned, raise it at the start of design. It affects the grade, the interior finish, and every metal component in contact with the water.
Stages 3 and 4: Cutting, Forming, and Welding
Once drawings are approved, stainless steel plate is cut to the panel dimensions and formed into walls, floor sections, steps, and corners. Forming a single sheet into multiple planes, rather than joining flat pieces, reduces the total length of weld seams in the finished shell.
Welding turns individual components into a continuous watertight structure. RenoSys TIG welds its SummitSeries vessels. TIG welding gives the welder precise control of heat input, which matters in stainless steel because excess heat around a weld can reduce corrosion resistance in the surrounding metal.
Larger in-ground pools are usually fabricated as sections sized for shipping. As an example, trade publication Athletic Business reported in 2024 that RenoSys delivers factory-welded corner assemblies to the job site along with 20-foot-wide wall sections, which are then welded together into a fully welded system.
Stage 5: Weld Finishing, Cleaning, and Passivation
Cutting, grinding, and welding can leave heat tint, embedded iron particles, and other surface contamination. If left in place, these can become starting points for rust staining or corrosion, even on a high-grade alloy.
Post-fabrication cleaning restores the surface. Passivation is one common method. ASTM A967 is the standard specification for chemical passivation treatments for stainless steel parts. It covers nitric acid, citric acid, and electrochemical treatments, along with tests to confirm free iron has been removed.
For specifiers, the practical step is to ask the manufacturer how welds are finished and cleaned, and how the result is verified. This applies to both shop welds and field welds made during installation.
Stage 6: Testing for Watertight Integrity
A welded shell should be proven watertight before the interior finish goes on and the pool is filled for operation. RenoSys performs static and pressure testing on each SummitSeries elevated pool project.
Where testing happens depends on how the shell ships. A vessel that ships whole can be tested before it leaves the shop. A pool assembled from sections has field welds, so it needs testing after assembly on site. Ask your manufacturer which tests are performed, at what stage, and how results are documented.
Stages 7 and 8: Shipping and Installation
Shipping format is often decided by logistics as much as engineering. Road transport limits, building access, crane or hoist capacity, and the route into the pool area all influence how large each section can be.
RenoSys ships SummitSeries vessels pre-assembled or in sections for assembly on site, depending on the project. Because the shell is fabricated off site, installation does not depend on concrete forming, pouring, or curing, and outdoor work is less sensitive to weather.
Scope on site is divided clearly. The general contractor handles excavation, site preparation, and the surrounding construction. On elevated projects, the building structure is designed by the structural engineer of record and built by the general contractor. RenoSys crews set, weld, and test the pool shell and install the RenoSys-manufactured components that go with it, such as stainless steel pool gutters.
Stage 9: Interior Finish Options
The interior finish is the surface swimmers touch and the surface that meets the water. RenoSys offers three interior options on its stainless steel vessels:
- Natural stainless steel. A clean, contemporary look, common on spas, cold plunges, and architectural pools.
- Ceramic tile. Often chosen to match a facility’s design standards or architectural finish palette.
- 60-mil PVC membrane. The RenoSys PVC pool shell is a textured, slip-resistant membrane that can include racing lanes, targets, and custom logos.
The finish decision also connects back to grade selection and water chemistry, so it should be made at the same time.
Questions to Ask a Stainless Steel Pool Manufacturer
Use these questions to compare manufacturers on a like-for-like basis:
- Which stainless steel grade do you recommend for this project’s water chemistry, and why?
- Where is the stainless steel sourced, and where is the shell fabricated?
- How are penetrations and fittings attached to the shell?
- Which welding process is used in the shop and in the field?
- How are welds finished and cleaned, and how is that verified?
- What testing is performed, at which stages, and how is it documented?
- Will the shell ship whole or in sections, and what does that require for site access and lifting?
- What exactly is in your installation scope, and what stays with the general contractor?
- What warranty covers the shell and the interior finish, and what are the conditions?
For a broader look at where stainless steel fits, see the pros and cons of stainless steel pools.
Stainless Steel Pool Shell FAQ
What grade of stainless steel is used for pool shells?
Most commercial stainless steel pool shells use 304L or 316L. Both are low-carbon grades suited to welding. 316L contains molybdenum, which gives it higher resistance to chloride pitting. Industry guidance recommends 304L for pool water up to 250 ppm chloride and 316L for up to 500 ppm, so source water chemistry should guide the choice.
Can a stainless steel pool shell be used with a saltwater system?
Not with common grades as the water-contact surface. The International Molybdenum Association advises that 304L and 316L should not be used for saltwater pool linings, ladders, or water handling equipment. If a saltwater system is planned, raise it early so the grade, interior finish, and metal components can be selected accordingly.
Is a stainless steel pool shell welded in the factory or on site?
Both, in most commercial projects. Components and sections are welded in the shop, where conditions are controlled. Larger pools ship in sections that are welded together on site. Smaller vessels, such as spas and cold plunges, can often ship fully assembled.
Why are stainless steel shells used for elevated and rooftop pools?
A welded stainless steel shell is watertight by construction and considerably lighter than cast-in-place concrete. It is fabricated off site, so it avoids forming and curing at height. Elevated pools still need a secondary containment system and a structure designed by the building’s engineer of record.
How long does it take to manufacture a stainless steel pool shell?
Lead time depends on pool size, design complexity, and the approval of shop drawings. Because fabrication happens off site, it can often proceed while excavation or structural work is underway, which helps compress the overall construction schedule. Ask for a fabrication schedule tied to drawing approval.
Talk Through Your Project With RenoSys
RenoSys has spent more than 38 years in commercial aquatics. It designs and manufactures its own American-made stainless steel pool components at its Indianapolis facility and installs them for municipalities, universities, hotels, and other commercial facilities across North America.
To discuss grade selection, shipping format, or scope for your project, request a free project evaluation or call 800.783.7005.