{
  "url": "https://openlegislation.uk/water-intended-for-human-consumption-private-supplies-scotland-regulations-2017/schedule-4/paragraph-3",
  "json_url": "https://openlegislation.uk/water-intended-for-human-consumption-private-supplies-scotland-regulations-2017/schedule-4/paragraph-3.json",
  "legislation": "ssi/2017/282",
  "legislation_title": "The Water Intended for Human Consumption (Private Supplies) (Scotland) Regulations 2017",
  "legislation_url": "https://openlegislation.uk/water-intended-for-human-consumption-private-supplies-scotland-regulations-2017",
  "path": "schedule/4/paragraph/3",
  "kind": "paragraph",
  "number": "3",
  "heading": null,
  "text": "Until 31st December 2019, the enforcing authority may, for a parameter in Table 2, use the corresponding ‘trueness’, ‘precision’ and ‘limit of detection’ in that table as an alternative set of performance characteristics (instead of using the limit of quantification and the uncertainty of measurement referred to in paragraph 1(1)).\nTABLE 1\nMinimum performance characteristic: uncertainty of measurement\nParameter\nUncertainty of measurement\n(% of parametric value, except pH) (Note 1)\nNotes\nAluminium\n25\nAmmonium\n40\nAntimony\n40\nArsenic\n30\nBenzo(a)pyrene\n50\nNote 5\nBenzene\n40\nBoron\n25\nBromate\n40\nCadmium\n25\nChloride\n15\nChromium\n30\nConductivity\n20\nCopper\n25\nCyanide\n30\nNote 6\n1,2-dichloroethane\n40\nFluoride\n20\nHydrogen ion concentration (in pH)\n0.2\nNote 7\nIron\n30\nLead\n25\nManganese\n30\nMercury\n30\nNickel\n25\nNitrate\n15\nNitrite\n20\nOxidisability\n50\nNote 8\nPesticides\n30\nNote 9\nPolycyclic aromatic hydrocarbons\n50\nNote 10\nSelenium\n40\nSodium\n15\nSulphate\n15\nTetrachloroethene\n30\nNote 11\nTrichloroethene\n40\nNote 11\nTrihalomethanes: total\n40\nNote 10\nTotal organic carbon\n30\nNote 12\nTurbidity\n30\nNote 13\nTABLE 2\nMinimum performance characteristics: trueness, precision and limit of detection\nParameter\nTrueness\n(% of parametric value, except for pH) (Note 2)\nPrecision\n(% of parametric value, except for pH) (Note 3)\nLimit of detection\n(% of parametric value, except for pH) (Note 4)\nNotes\nAluminium\n10\n10\n10\nAmmonium\n10\n10\n10\nAntimony\n25\n25\n25\nArsenic\n10\n10\n10\nBenzo(a)pyrene\n25\n25\n25\nBenzene\n25\n25\n25\nBoron\n10\n10\n10\nBromate\n25\n25\n25\nCadmium\n10\n10\n10\nChloride\n10\n10\n10\nChromium\n10\n10\n10\nConductivity\n10\n10\n10\nCopper\n10\n10\n10\nCyanide\n10\n10\n10\nNote 6\n1,2-dichloroethane\n25\n25\n10\nFluoride\n10\n10\n10\nHydrogen ion concentration (in pH)\n0.2\n0.2\nNote 7\nIron\n10\n10\n10\nLead\n10\n10\n10\nManganese\n10\n10\n10\nMercury\n20\n10\n20\nNickel\n10\n10\n10\nNitrate\n10\n10\n10\nNitrite\n10\n10\n10\nOxidisability\n25\n25\n10\nNote 8\nPesticides\n25\n25\n25\nNote 9\nPolycyclic aromatic hydrocarbons\n25\n25\n25\nNote 10\nSelenium\n10\n10\n10\nSodium\n10\n10\n10\nSulphate\n10\n10\n10\nTetrachloroethene\n25\n25\n10\nNote 11\nTrichloroethene\n25\n25\n10\nNote 11\nTrihalomethanes: total\n25\n25\n10\nNote 10\nTurbidity\n25\n25\n25\nNotes to Table 1 and Table 2\nNote 1: Uncertainty of measurement is a non-negative parameter characterising the dispersion of the quantity values being attributed to a measurand, based on the information used. The performance criterion for measurement uncertainty (k = 2) is the percentage of the parametric value stated in the table or better. Measurement uncertainty must be estimated at the level of the parametric value, unless otherwise specified.\nNote 2: Trueness is a measure of systematic error, i.e. the difference between the mean value of the large number of repeated measurements and the true value. Further specifications are those set out in international standard ISO 5725 entitled “Accuracy (trueness and precision) of measurement methods and results”.\nNote 3: Precision is a measure of random error and is usually expressed as the standard deviation (within and between batches) of the spread of results from the mean. Acceptable precision is twice the relative standard deviation. This term is further specified in international standard ISO 5725 entitled partly “Accuracy (trueness and precision) of measurement methods and results”.\nNote 4: Limit of detection is either three times the standard deviation within a batch of a natural sample containing a low concentration of the parameter, or five times the standard deviation of a blank sample (within a batch).\nNote 5: If the value of uncertainty of measurement cannot be met, the best available technique should be selected (up to 60 %).\nNote 6: The method determines total cyanide in all forms.\nNote 7: Values for trueness, precision and uncertainty of measurement are expressed in pH units.\nNote 8: Reference method European standard EN ISO 8467:1995 entitled “Water quality - Determination of permanganate index (ISO 8467:1993)”.\nNote 9: The performance characteristics for individual pesticides are given as an indication. Values for the uncertainty of measurement as low as 30 % can be achieved for several pesticides, higher values up to 80 % may be allowed for a number of pesticides.\nNote 10: The performance characteristics apply to individual substances, specified at 25 % of the parametric value in Table B.\nNote 11: The performance characteristics apply to individual substances, specified at 50 % of the parametric value in Table B.\nNote 12: The uncertainty of measurement should be estimated at the level of 3 mg/l of the total organic carbon in accordance with European standard EN 1484:1997 entitled “Water analysis - Guidelines for the determination of total organic carbon and dissolved organic carbon”.",
  "extent": "S",
  "status": null,
  "version": "current",
  "annotations": [
    {
      "type": "F",
      "label": "F1",
      "text": "Word in sch. 4 para. 3 substituted (26.10.2017) by The Public and Private Water Supplies (Miscellaneous Amendments) (Scotland) Regulations 2017 (S.S.I. 2017/321), regs. 1, 4(7)(a)"
    },
    {
      "type": "F",
      "label": "F2",
      "text": "Word in sch. 4 para. 3 Table 1 substituted (26.10.2017) by The Public and Private Water Supplies (Miscellaneous Amendments) (Scotland) Regulations 2017 (S.S.I. 2017/321), regs. 1, 4(7)(b)"
    },
    {
      "type": "F",
      "label": "F3",
      "text": "Word in sch. 4 para. 3 Table 2 substituted (26.10.2017) by The Public and Private Water Supplies (Miscellaneous Amendments) (Scotland) Regulations 2017 (S.S.I. 2017/321), regs. 1, 4(7)(c)"
    },
    {
      "type": "I",
      "label": "I1",
      "text": "Sch. 4 para. 3 in force at 27.10.2017, see reg. 1(1)"
    },
    {
      "type": "footnote",
      "label": "f1",
      "text": "Acrylamide, epichlorohydrin and vinyl chloride to be controlled by product specification."
    },
    {
      "type": "footnote",
      "label": "f2",
      "text": "Acrylamide, epichlorohydrin and vinyl chloride to be controlled by product specification."
    },
    {
      "type": "footnote",
      "label": "f3",
      "text": "This standard has been approved by the International Organization for Standardization (ISO). Under reference BS ISO 5725-1 to BS ISO 5725-6, these are published as UK standards by the British Standards Institution."
    },
    {
      "type": "footnote",
      "label": "f4",
      "text": "This standard was approved by the European Committee for Standardization (CEN) on 3rd November 1994. Under reference EN ISO 8467:1995, it is published as a UK standard by the British Standards Institution (ISBN 0 580 23435 5)."
    },
    {
      "type": "footnote",
      "label": "f5",
      "text": "This standard was approved by the European Committee for Standardization (CEN) on 6th April 1997. Under reference BS EN 1484:1997, it is published as a UK standard by the British Standards Institution (ISBN 0 580 28372 0)."
    }
  ],
  "outstanding_effects": [],
  "provenance": {
    "source": "legislation.gov.uk",
    "source_url": "https://www.legislation.gov.uk/ssi/2017/282/schedule/4/paragraph/3",
    "retrieved_at": "2026-10-28T21:17:02.229514+00:00"
  },
  "licence": "Open Government Licence v3.0",
  "licence_url": "https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/",
  "attribution": "Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives."
}