What Makes a Defensible Pool Slip Report

Accreditation as the foundation

UKAS ISO/IEC 17025 accreditation is the single most important defensive feature of a pool pendulum report. A non-accredited report can be challenged on technical-competence grounds before its substantive findings are even discussed; an accredited report carries the implicit verification of the lab's methodology, calibration, traceability and quality system.

For pool reports specifically, the lab's UKAS scope must explicitly cover pendulum testing using Slider 55 — the appropriate slider for barefoot pool environments. A laboratory accredited only for Slider 96 work is not appropriate for pool surround testing regardless of other claims of accreditation.

Mandatory report content

A defensible pool pendulum report contains, as a minimum:

• Identification of the testing organisation and its UKAS schedule reference
• Identification of the pool/property tested and the date of testing
• Identification of who instructed the testing and on what basis
• The standard followed (BS EN 16165:2021 Annex C, with note of historical BS 7976-2 where the specification still references it)
• The instrument used (model, serial number, calibration validity)
• The slider(s) used (Slider 55 for barefoot zones, plus Slider 57 or 96 for any sock/shod zones)
• The calibration sequence followed on the test day
• The slider conditioning protocol used between test sets
• For each test location: location description (with reference to a plan or photograph), contamination conditions (wet with clean water as standard, plus any supplementary contaminant), individual swing readings per direction, calculated mean PTV
• Photographic record of each test location
• Surface roughness Rz data where included
• Pool plant chemistry record at the time of testing (chlorine residual, pH, calcium hardness)
• Discussion and findings written in unbiased language
• The technical signatory's name, position and signature
• Any limitations or caveats explicitly identified

Photographs are evidence

Each pool test location should be photographed before testing — capturing the surround as found, the lighting, any contamination present, the drain locations, and the surrounding scene. These photographs are evidence in their own right and are routinely scrutinised by opposing experts in pool litigation. A report without location photographs is weaker, not just less attractive.

Methodology disclosure

The pool report should make explicit:

• Which standard the methodology follows (and any deviations)
• How test locations were selected (representative sample, specific incident location, full-zone coverage)
• Whether testing was carried out post-clean, mid-cycle, end-of-day
• Whether the pool was in normal operating chemistry or any non-standard state
• Whether any preparation was done to the surface and why
• The footwear/slider assumption and any rationale

Raw data, not just conclusions

Reports that quote only an overall pass/fail or a single rounded PTV per area are evidentially weak. Defensible pool reports include the raw swing readings — every individual swing, in every direction, at every location, wet — so that the next reviewer can verify the calculation and assess scatter within each test set. Compliant UKAS reporting includes raw data as a matter of course.

Unbiased language

The pool report's prose should describe, not advocate. 'The surround achieved a wet PTV of 28 (Slider 55) at this location, placing it in the moderate slip-potential band per HSE guidance' is defensible. 'The surround is dangerous and unfit for pool use' is advocacy and undermines the report's standing under CPR Part 35. Where conclusions need to be drawn, they should be in the conclusions section, separated from the data, and qualified as the expert's opinion.

Limitations, explicitly

Defensible pool reports state their limitations:

• Locations not tested and why (operational access, lifeguard cover, programme constraints)
• Pool plant chemistry conditions at the time of testing (any departures from normal operating ranges)
• Time elapsed since the incident (in post-incident testing)
• Any equipment or methodology departures from standard practice
• The expert's own areas of expertise relative to the matter at hand

An expert who acknowledges limitations is more credible than one who claims complete knowledge of every aspect.

CPR Part 35 compliance, where relevant

For reports likely to be used in pool litigation, full CPR Part 35 compliance should be built in from the outset — overriding duty statement, expert qualifications, statement of instructions, statement of truth. Adding these later is harder than including them from the first draft.