The original intent of PHTA-6 was straightforward: establish a standard covering both the construction and installation requirements for residential portable spas and swim spas. Over time, however, the industry found itself navigating an increasingly complex landscape.
While PHTA-6 contained construction requirements, UL 1563 evolved into a comprehensive product construction standard that also addressed many site-specific considerations where appropriate. Both PHTA-6 and UL 1563 are ANSI (American National Standards Institute) standards, and both share the same objective — promoting the safe construction, installation, and operation of residential portable spas. However, each standard organized and addressed technical requirements differently.
This overlap created unintended challenges.
In several jurisdictions, local authorities adopted APSP-6 (now PHTA-6) into code and required portable spas to be certified to that standard. The difficulty was that certification bodies generally were not accredited to certify products to APSP-6. Instead, manufacturers relied on UL 1563, the nationally recognized product safety standard supported by accredited testing and certification organizations.
As a result, manufacturers occasionally found themselves in the impossible position of being required to obtain a certification that was not realistically available — even though their products had already been evaluated to recognized safety standards such as UL 1563. In some cases, this led to delays, confusion, and even lost sales.
Recognizing the need for greater clarity, industry stakeholders came together to develop a practical solution.
The goal was to better distinguish product construction requirements from site-specific installation requirements. Construction-related provisions, along with applicable site-specific requirements that fall within the scope of product safety certification, would move into UL 1563. PHTA-6 would then focus on installation requirements and other site-specific provisions more appropriately addressed through code enforcement than product certification.
The harmonization effort formally began in 2023 following a request from Nathan Coelho, on behalf of PHTA, to the committee responsible for maintaining UL 1563. Under the leadership of Steve Macey, the UL 1563 task group conducted a comprehensive review of every applicable provision within APSP-6.
The now-complementary standards, UL 1563 and a streamlined PHTA-6, provide clearer division of responsibilities and minimize confusion for builders of portable spas and swim spas.
Where equivalent requirements already existed in UL 1563, no changes were necessary. Where relevant APSP-6 provisions were absent — and fell within the scope of product certification — the task group developed proposals for inclusion in UL 1563. Through this collaborative process, all applicable construction requirements and related provisions from APSP-6 were evaluated and incorporated where appropriate. The resulting Seventh Edition of UL 1563, published in January 2025, includes the adopted provisions from APSP-6 (PHTA-6) as part of the ANSI national standard.
With that phase complete, attention turned to revising PHTA-6 itself.
Again chaired by Steve Macey, the PHTA-6 Standards Writing Committee systematically reviewed the document section by section. Requirements already addressed within UL 1563 were proposed for removal, as were construction provisions now covered by the product standard. Requirements that remained uniquely site-specific — and outside the intended scope of UL 1563 — were retained.
The result is a complementary pair of standards: a strengthened UL 1563 that now incorporates key construction provisions from PHTA-6, and a streamlined PHTA-6 that focuses on installation requirements and code-related considerations. This clearer division of responsibilities reduces overlap, minimizes confusion, and better reflects the intended purpose of each standard.
The revised PHTA-6 is currently progressing through the standards development process, and feedback received thus far has been overwhelmingly positive. Once finalized, it will continue to address important site-specific requirements for portable spas and swim spas while relying on UL 1563 as the primary product certification standard. It will also retain provisions related to barriers, energy efficiency through PHTA-14, and other installation considerations unique to portable spas.
Most importantly, the revised framework provides greater clarity for everyone involved. Manufacturers, certification bodies, regulators, dealers, installers, and consumers all benefit when standards clearly define their purpose and work together rather than overlap.
This harmonization effort demonstrates what can be accomplished when industry stakeholders collaborate to solve real-world challenges. By aligning two important standards while respecting their distinct roles, the industry has created a stronger, more practical framework that will benefit manufacturers, regulators, installers, and consumers for years to come.
