# Methodology

> How Walk-In Tub Lab researches costs, methods and regulations: sources, cost models and limits.

Canonical: https://walkintublab.com/methodology/

Last updated: 2026-11-08

Every number on this site is either sourced or labelled as an estimate. This
    page explains the difference, and how a claim gets from a source document to a
    published page.

## 1. Primary sources first

    For a tub we work from the manufacturer's spec sheet and installation manual:
    exterior and interior dimensions, seat height, step-in threshold, water
    capacity, door-seal design and the electrical requirement. For accessibility
    dimensions we use ICC/ANSI A117.1 and published ADA guidance. For labour and
    permit questions we use the state licensing board and the local permit office
    named on the city page.

## 2. Cost models show their inputs

    Installed cost is modelled from visible inputs: the material or equipment
    price, the labour and access scope (excavation, drain, electrical, permit),
    consumables, and a reserve for service or repair. We do not present a single
    "average cost" as if it were a quote; the range and what it includes are stated
    on the page.

## 3. How options are compared

    We compare step-in height, seat and transfer options, door-seal design and
    serviceability, water capacity against the household's hot-water supply, and
    the warranty's exclusions. A product earns a recommendation when it meets the
    stated criteria for a stated need; it cannot buy a place in a ranking.

## 4. What we have not tested

    We do not run a laboratory or a crew, and we do not carry out every job we write
    about. When a claim comes from a manufacturer document, an adopted code, a
    certification listing or a contractor report, we say which. We do not imply
    first-hand testing we did not perform.

## 5. Sources we work from

     |
       | Source type | What it decides | How it is cited

       | Manufacturer spec sheets and installation manuals | Dimensions, seat height, water capacity, door-seal design | Spec reproduced with the model named

       | ICC/ANSI A117.1 and published ADA guidance | Accessible-bath dimensions and clearances | Standard or guidance named

       | State licensing boards | Which trade may do the plumbing and electrical work | Board named, with its lookup link

       | Local permit offices | Whether a tub replacement needs a permit and inspection | Office named, with its link

       | Published US price guides | Installed cost bands | Band with the month it was checked

    When two sources disagree, the page says which one it followed and why. A
    figure that cannot be traced to a document is labelled an estimate, and an
    estimate is never presented as the price of a specific job.

## 6. Listings and directory data

    The service-area directory is compiled from public business records: the
    firm's own website, its published address and phone number, and the state or
    city licence register named on the city page. A record is marked verified only
    when the name, address, phone and licence have been checked against those
    sources and the date of the check recorded; everything else is labelled. Where
    a source does not publish a ZIP code or a website, the field is left blank
    rather than guessed, and the page says "not published".

## 7. Corrections

    If a code, a specification or a listing changes, we update the article and its
    "last updated" date. Email
    [contact@walkintublab.com](mailto:contact@walkintublab.com) with the page and the correction.