{
  "url": "https://openlegislation.uk/private-water-supplies-regulations-1991/schedule-2",
  "json_url": "https://openlegislation.uk/private-water-supplies-regulations-1991/schedule-2.json",
  "legislation": "uksi/1991/2790",
  "legislation_title": "The Private Water Supplies Regulations 1991",
  "legislation_url": "https://openlegislation.uk/private-water-supplies-regulations-1991",
  "path": "schedule/2",
  "kind": "schedule",
  "number": "2",
  "heading": "PRESCRIBED CONCENTRATIONS OR VALUES",
  "text": "Table A\nItem\nParameters\nUnits of Measurement\nConcentration or Value (maximum unless otherwise stated)\nNote: (i) If silver is used in a water treatment process, 80 may be substituted for 10.\n1.\nColour\nmg/1 Pt/Co scale\n20\n2.\nTurbidity (including suspended solids)\nFormazin turbidity units\n4\n3.\nOdour (including hydrogen sulphide)\nDilution number\n3 at 25°C\n4.\nTaste\nDilution number\n3 at 25°C\n5.\nTemperature\n°C\n25\n6.\nHydrogen ion\npH value\n9.5\n5.5 (minimum)\n7.\nSulphate\nmg SO4/1\n250\n8.\nMagnesium\nmg Mg/1\n50\n9.\nSodium\nmg Na/1\n150\n10.\nPotassium\nmg K/1\n12\n11.\nDry residues\nmg/1\n1500 (after drying at 180°C)\n12.\nNitrate\nmg NO3/1\n50\n13.\nNitrite\nmg NO2/1\n0.1\n14.\nAmmonium (ammonia and ammonium ions)\nmg NH4/1\n0.5\n15.\nKjeldahl nitrogen\nmg N/1\n1\n16.\nOxidisability (permanganate value)\nmg O2/1\n5\n17.\nTotal organic carbon\nmg C/1\nNo significant increase over that normally observed\n18.\nDissolved or emulsified hydrocarbons (after extraction with petroleum ether); mineral oils\nμg/1\n10\n19.\nPhenols\nμg C6H5OH/1\n0.5\n20.\nSurfactants\nμg/1 (as lauryl sulphate)\n200\n21.\nAluminium\nμg Al/1\n200\n22.\nIron\nμg Fe/1\n200\n23.\nManganese\nμg Mn/1\n50\n24.\nCopper\nμg Cu/1\n3000\n25.\nZinc\nμg Zn/1\n5000\n26.\nPhosphorus\nμg P/1\n2200\n27.\nFluoride\nμg F/1\n1500\n28.\nSilver\nμg Ag/1\n10(i)\nTable B\nItem\nParameters\nUnits of Measurement\nMaximum Concentration\nNote:\n(i) The sum of the detected concentrations of individual substances.\n(ii) The sum of the detected concentrations of fluoranthene, benzo 3.4 fluoranthene, benzo 11.12 fluoranthene, benzo 3.4 pyrene, benzo 1.12 perylene and indeno (1,2,3-cd) pyrene.\n1.\nArsenic\nμg As/1\n50\n2.\nCadmium\nμg Cd/1\n5\n3.\nCyanide\nμg CN/1\n50\n4.\nChromium\nμg Cr/1\n50\n5.\nMercury\nμg Hg/1\n1\n6.\nNickel\nμg Ni/1\n50\n7.\nLead\nμg Pb/1\n50\n8.\nAntimony\nμg Sb/1\n10\n9.\nSelenium\nμg Se/1\n10\n10.\nPesticides and related products:\n(a) individual substances\nμg/1\n0.1\n(b) total substances(i)\nμg/1\n0.5\n11.\nPolycyclic aromatic hydrocarbons(ii)\nμg/1\n0.2\nTable C\nItem\nParameters\nUnits of Measurement\nMaximum Concentration\nNote: (i) Analysis by multiple tube method.\n1.\nTotal coliforms\nnumber/100 ml\n0\n2.\nFaccal coliforms\nnumber/100 ml\n0\n3.\nFaccal streptococci\nnumber/100 ml\n0\n4.\nSulphite-reducing clostridia\nnumber/20 ml\n≤1(i)\n5.\nColony counts\nnumber/1 ml at 22°C or 37°C\nNo significant increase over that normally observed\nTable D(i)\nItem\nParameters\nUnits of Measurement\nMaximum Concentration or Value\nNote: (i) See regulation 3(3)(d).\n1.\nConductivity\nμS/cm\n1500 at 20°C\n2.\nChloride\nmg Cl/1\n400\n3.\nCalcium\nmg Ca/1\n250\n4.\nSubstances extractable in chloroform\nmg/1 dry residue\n1\n5.\nBoron\nμg B/1\n2000\n6.\nBarium\nμg Ba/1\n1000\n7.\nBenzo 3,4 pyrene\nμg/1\n10\n8.\nTetrachloromethane\nμg/1\n3\n9.\nTrichloroethene\nμg/1\n30\n10.\nTetrachlorothene\nμg/1\n10\nTable E\nItem\nParameters\nUnits of Measurement\nMinimum Concentration(i)\nNote: (i) See regulation 3(4).\n1.\nTotal hardness\nmg Ca/1\n60\n2.\nAlkalinity\nmg HCO3/1\n30",
  "extent": null,
  "status": null,
  "version": "current",
  "annotations": [],
  "outstanding_effects": [],
  "provenance": {
    "source": "legislation.gov.uk",
    "source_url": "https://www.legislation.gov.uk/uksi/1991/2790/schedule/2",
    "retrieved_at": "2026-10-29T14:32:48.534038+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."
}