The American National Standards Institute (ANSI) has adopted as a standard performance requirements for pitless adapters, pitless units and well caps codeveloped by the Water Systems Council (WSC) and ASSE International.

“WSC and I are pleased to have worked together with ASSE to bring this standard into an ANSI-accredited consensus process,” says John Surinak, president of Maass Midwest Mfg. Inc. and chair of the ASSE 1093/PAS-97 Working Group. “This most recent revision to WSC PAS-97 clarified pitless adapter and pitless unit definitions, revised the pitless adapter and pitless unit testing, and revised the sanitary well cap watertight capability testing. Separate tests for surface water contamination and internal pressure for pitless adapters, and similar tests for pitless units were also developed.”

The WSC first established a standard for pitless adapters and pitless units in 1966, followed by the development of a standard for well caps in 1988. A combined standard, PAS-97, was adopted in 1997. In 2019, WSC's PAS-97 Working Group co-developed a revision of the PAS-97 standard with the Product Standards Committee of ASSE International in order to meet ANSI accreditation requirements.

Pitless adapters and pitless units are devices designed to attach to openings in the water well casing. When properly installed, they provide sanitary connections by preventing the entrance of contaminants from surface or near-surface sources through such openings into the well or potable water supply, and permit the termination of the well above the ground surface.

Performance requirements in ASSE 1093-2019/WSC PAS-97(2019) include compliance testing for water contamination and internal pressure of pitless adapters and pitless units, tamper resistance, water resistance, vermin and contaminant/pollutant resistance, and venting of sanitary well caps, among other detailed requirements.

To purchase ASSE 1093-2019/WSC PAS-97(2019), visit Water Well Standards page on the WSC website.

ASSE International is an ANSI-accredited standards developer and product certification body composed of members representing all disciplines of the plumbing and mechanical industries. The group’s standards and professional certifications aim to improve the performance and safety of plumbing and mechanical systems. Learn more at

The Water Systems Council works to protect groundwater and to ensure private well users in the United States have safe, reliable drinking water. For more information, visit