Source: https://guthlabs.ai/docs/instruments/water-hardness-calculator-ppm-caco3/implementation/

instrument implementation / implementation-contract

# Water Hardness Calculator (ppm CaCO3) implementation

A source-bound implementation contract for Water Hardness Calculator (ppm CaCO3); deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t5-058

**Effect**: Computation or source lookup only

## Input and validation requirements

The plain-arithmetic implementation is vulnerable to non-finite results for extreme concentrations and may also accept physically invalid negative concentrations, producing a misleading hardness value and classification.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "Ca2_mg_L": 20,
    "Mg2_mg_L": 10
  },
  "expected_outputs": {
    "hardness_ppm_CaCO3": 91,
    "classification": "moderately hard"
  },
  "working": "Ca contribution = 2.5 x 20 = 50 mg/L as CaCO3. Mg contribution = 4.1 x 10 = 41 mg/L as CaCO3. Total hardness = 50 + 41 = 91 mg/L, numerically 91 ppm. Since 60 < 91 <= 120, classification = moderately hard."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/water-hardness-calculator-ppm-caco3/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/water-hardness-calculator-ppm-caco3/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/water-hardness-calculator-ppm-caco3/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche5/tranche5-results.json`