The control of legionellosis including legionnaires’ disease HealthandSafetySeriesbookletHS(G)70 1 R£irfcKitiv»i& m | I TM1S*t*«C 1 funmm?mnotuwmm J PrintedimagedigitisedbytheUniversityofSouthamptonLibraryDigitisationUnit ©Crowncopyright1991 Firstpublished1991 HS(G)series Thepurposeofthisseriesistoprovideguidancefor thosewhohavedutiesundertheHealthandSafetyat WorketcAct1974andotherrelevantiegislation.Itgives guidanceonthepracticalapplicationoflegislation,butit shouldnotberegardedasanauthoritativeinterpretation ofthelaw. FurtheradviceonthisoranyotherHSEpublicationmay beobtainedfromareaofficesofHSEorfromthepublic enquirypointslistedbelow. HealthandSafetyExecutive LibraryandInformationServices BroadLane SHEFFIELDS37HQ Tel:(0742)752539Telex:54556 HealthandSafetyExecutive LibraryandinformationServices BaynardsHouse 1 ChepstowPlace WestbourneGrove LONDONW24TF Tel:071-221 0870Telex:25683 ISBN011 885660X PrintedimagedigitisedbytheUniversityofSouthamptonLibraryDigitisationUnit 1 6 CONTENTS Introduction 1 Microbiology 1 Medicalaspects 1 Samplingforiegionella 2 Legislation 2 Identificationandassessmentofrisk 3 Drawingupandapplyingprecautions 3 Managementandtheresponsibilitiesandcompetenceofpersonnel 4 Recordkeeping 4 Responsibilitiesofmanufacturers,importers,suppliersandinstallers Hotandcoldwaterservices 5 Therisk 5 Precautions 7 Selectionofmaterials 7 Systemdesignandconstruction 7 Operation 7 Routineinspectionandmaintenance 8 Cleaninganddisinfection 8 Records 9 Airconditioningandindustrialcoolingsystems 9 Therisk 9 Alternativemethodsofcooling 11 Precautions 1 Coolingtowerposition 12 Designandconstruction 12 Airconditioningductworkandplant 12 Commissioning,operationandmaintenance 12 Cleaninganddisinfection 14 Freeresidualchlorine 15 Watertreatmentofcoolingsystems 15 Settingupthewatertreatmentregime 16 Alternativemethodsofwatertreatment 1 Dissolvedsolids 16 Monitoringandroutinechecking 16 Records 17 Spasandwhirlpoolbaths 18 Humidifiersandairwashers 18 Protectionofpersonnel 18 Actionintheeventofanoutbreak 19 Furtherguidance 19 III PrintedimagedigitisedbytheUniversityofSouthamptonLibraryDigitisationUnit INTRODUCTION 5 Theecologyoflegionellainwatersystemsisnot fullyunderstood.However,thefollowingconditionshave 1 ThisbookletreplacesGuidanceNoteEH48 beenfoundtoaffectitsrateofgrowth: TLrrheeeigscsieooagpnrnuncibahsliiercidnaettsioin’otndEh,iHesHde4Sia8(ssGeet)ahp7asut0eb,rlaeitnvshdihesreiiedtosfniocnwraeoJuuarslneefduslaebrcpetyrson1gte9hrci8ese7ss.sseIadtr.wyaass (a) fwbaaevtloeourwrt2ge0rm°opCwe,trhaa.tnuIdtrieistsduionnectsohenmomrtoasnnugretvoiovffien2da0bptoroovl4ei5f6e°r0Ca°tCi.on progressandtakesaccountofthecircumstances Theoptimumlaboratorytemperatureforthegrowth concerningtheoutbreaksandcasesoflegionnaires’ ofthebacteriumis37°C.Organismsmay,however, tdhiissedaisseetahsaetahnadveitoscccauursreesdissinstcilel1a9d8v7a.ncKinnogwsloedtghaetof wrehmeaninthdeotremmapnetraintucroeolrweaatcehre,smualtsiupiltyaibnlgeolenvleyl; furtherrevisionmaybenecessary. (b) thepresenceofsediment,sludge,scaleand organicmaterialcanactasasourceofnutrients 2 Thefirstidentifiedoutbreakoflegionnaires' forlegionella; diseaseoccurredamongpeoplewhohadattendeda PennsylvaniaStateConventionoftheAmericanLegion (c) legionellahavebeenshowntocolonisecertain in1976.Anapparentlynewbacteriumwasisolatedfrom typesofwaterfittings,pipeworkandmaterials lungspecimens.Retrospectiveexaminationofstored usedintheconstructionofwatersystems.The specimensfrompreviouslyunsolvedoutbreaksof presenceofsuchmaterialsmayprovidenutrients respiratoryillnessrevealedthatsomeofthesecases forlegionellaandcanmakeeradicationdifficult; werealsocausedbythebacteriumnowknownas Legionellapneumophila.In1976thediseasewas (d) commonlyencounteredorganismsinwater thereforenotnewbutnewlyrecognised. 7 systemssuchasalgae,amoebaeandother bacteriamayserveasanadditionalnutrient 3 L.pneumophilacanalsocauseashortfebrile sourceforlegionella.Algalslimemayprovidea (feverish)illnesswithoutpneumoniaknownasPontiac stablehabitatformultiplicationandsurvival. fever.SinceL.pneumophilawasoriginallyisolated Legionellacangrowinprotozoaandithasbeen severalotherspeciesoflegionellacapableofcausing showntoproliferaterapidlyinwaterborne pneumoniahavebeendescribedintheUKandelsewhere. amoebae; The1988outbreakofnon-pneumoniclegionellosisat LochgoilheadinScotland,nowreferredtoas (e) theformationofabiofilmwithinawatersystemis Lochgoilheadfever,wasattributedtothespecies thoughttoplayanimportantroleinharbouringand cL.ovmeircdlaedgeiio.nnLaeigrieosn’edlilsoesaissei,stPhoentgieancerfievcetrearnmdusedto cpraonvigdrionwg.fAavboiuorfailbmleiscaonldaiyteironosfimnicwrhoi-cohrgleagniiosnmelsla Lochgoilheadfever. containedinamatrixwhichmayformaslimeop surfacesincontactwithwater.Incorporationof legionellainbiofilmsandenclosurewithinprotozoa MICROBIOLOGY canprotecttheorganismsfromconcentrationsof biocidesthatwouldotherwisekillorinhibitthose 4 Legionellaisthenamegiventoagenusof organismsfreelysuspendedinwater. bacteriaofwhichL.pneumophilaisonespecies.Under themicroscopelegionellaappearrod-shaped.Legionella 6 InthelaboratoryL.pneumophilaisrecoveredfrom organismsarewidespreadinnaturalwatersourcesand concentratedwatersamplesbypropagationofthe havebeenfoundinrivers,lakes,streams,mudandsoil organismonaspeciallysupplementednutrientgrowth aswellasman-madewatersystems.Todate,atleast34 medium.Suchsamplesarenormallythenincubatedat differentspeciesoflegionellaarerecognised.The around37°C;itmaytakeuptosevendaysforcolonies speciesmostcommonlyassociatedwithdisease oflegionellatoinitiallyappear.Legionellacanbe outbreaksisL.pneumophila,whichisapparentlythe recognisedbyvisualexaminationofthecolonies mostpathogenicofthegenus.Fourteendifferent followedbyanumberoflaboratorytechniquestoidentify serogroupsofL.pneumophilahavebeendescribed. speciesandserogroup. L.pneumophilaserogroup1 isthemostcommonly associatedwithcasesoflegionnaires’diseaseintheUK althoughotherserogroupshavebeenassociatedwith MEDICALASPECTS outbreaksworldwide.Severalotherspeciesoflegionella havebeenfoundtocauseapneumoniatypeillness, Legionnaires’diseaseisatypeofpneumonia. iL.ncmliucddinagdeLi..feeleiand,aspreviouslymentioned, eBfefseicdtsesonafoftechteirngortghaenlsuonfgsthitembaodyy.alIsnofehcatvioensiesrciaouussed 1 PrintedimagedigitisedbytheUniversityofSouthamptonLibraryDigitisationUnit byinhalingairbornedropletsorparticlescontaining countryareoftensporadiccasesforwhichnosourceof viableiegionellawhicharesmallenoughtopassdeep infectionistraced.Howeverclustersofcaseshave intothelungsandbedepositedinthealveoli.Thereis occurred,forexample,outbreaksassociatedwithhotels, noevidencethatthediseaseistransmittedbyingestion factories,hospitalsandotherestablishmentssuchas orfrompersontoperson.Thedoseofiegionella thoseassociatedwithrecentoutbreaksinLondon. requiredtoinfectmanisnotknownandthereisreported tobea1%attackrate,sothatforevery100persons exposedgenerallyonlyonewilldevelopsymptomsof SAMPLINGFORLEGIONELLA disease.Legionnaires’diseasecanhaveanincubation periodoftwototendaysbutismoreusuallythreetosix 11 AsIegionellaarecommoninnaturalwater days.Malesaremorelikelytobeaffectedthanfemales sources, randomsamplingofwatersystemsand obcycaurrraetidoionftahbeo4u0tt3o:17.0Moyesatrraegpoergtreoducp.asAelsthhoauvgeh sEevrevnicwehsefroertshaempblaicntegrrieusmulwtisllaorfetennegyaitelidvepotshietrieveisrensoults. healthyindividualsmaydeveloplegionnaires’disease, guaranteethatitisnotpresentelsewhereinthesystem. peoplethoughttobeatanenhancedriskofinfection ThedoseofIegionellarequiredtoinfectman,the includesmokers,alcoholicsandpatientswithcancer, variationinresponseofexposedindividualsandthe chronicrespiratoryorkidneydisease.Thecasefatality variationinpathogenicityofdifferentstrainsarenotfully rateisapproximately12%butinimmunosuppressed understood.Itisthereforedifficulttodeterminerisksolely patientsorthosewithotherunderlyingdiseasethis onthebasisofwatersamplingresults.Forthesereasons, figuremaybehigher.Legionnaires’diseasemaybe randomwatersamplingforIegionellaisnotadvocated. treatedeffectivelywithseveralantibioticsincluding erythromycinandrifampicin.Recentexperimentshave 12 Samplingforiegionellaisseparateanddifferent showntheeffectivenessofazithromycin. fromsamplingtoassesswaterquality(paragraph118 refers).WatersamplingforIegionellamaysometimesbe 8highfeIvneitri,alchsiyilms,pthoemasdaocfhleegainodnnamiursecsl’edipsaiena.seAidnrcylude rmeeqausiurerdestosmuocnhitaosrathweateefrfitcraceyatomfepnrtercaeugtiimoenaorrytotrace wciotuhgbhresaotohnindge.vAebloopust,aatnhdirdmoosftpaptaiteinetnstsalssufofderevdeiflfoipculty tshuietsaboluercperootfocaonlibnyfepcetioopnl.eItwshhooualrdebceomcparertieendtouatndtoa diarrhoeaorvomitingandabouthalfbecomeconfused experiencedinsamplingforIegionellaandinterpreting ordelirious.Legionnaires’diseasemaynotalwaysbe results,itisespeciallyimportantthatanydecisionto severeandincommunityoutbreaksmildcasesmaybe sampleshouldnotdivertresourcesfromprecautionary recognisedwhichwouldprobablyhaveescaped measures,andnegativeresultsshouldnotleadto detectionexceptfortheincreasedawarenessofthe complacencyorarelaxationofstandards. diseaseinsuchasituation. 13 Coolingtowersandassociatedwatersystems wT9inhhcieucbhialtEliinxseopasnosmspuieuslrrudieaeolrdtlocyoofIlneadbgsiiettostinwoebelneletoanfwcefaaeicnvnuetltheewoaooudnrasstenoatdPnowtdinhttrthiehaeracendefaeydvsae.yrs. sacinohsnomtpuoralorrdltebsodcfeeattlsahiuineblgjw,ieanccttpoeratrrrootarsrgoieruoaatntpimnaheesnndmt1o1fpno6irutlotoiognrrg1i.2an3gmT.hmoifeswdiaestsceiorgnnqsueiaddleittroyed However,inanoutbreakinLochgoilheadinScotlandin 1988(referredtoasLochgoilheadfever)theincubation LEGISLATION periodwaslongerandinsomecasesuptoninedays. Symptomsalsolastedlongerinsomecases(upto14 14 TheControlofSubstancesHazardoustoHealth days)andinsomepatientsthesymptomsrecurred.The Regulations1988(COSHH)relatetotherisksfrom symptomsofPontiacfeveraresimilartothoseof hazardousmicro-organisms,includingiegionellaand moderatetosevereinfluenza:headache,tiredness, chemicalssuchasbiocidesandchlorine.Underthese fever,arthralgiaandmyalgiaand,inasmallproportionof Regulationsriskassessmentsandtheadoptionof cases,nausea,vomitingandcoughing.Nodeathshave appropriateprecautionsarerequiredtobemade. beenreported.Ahighpercentageofthoseexposedto riskdevelopPontiacfever,which,aspreviously 15 TheApprovedCodeofPracticeThepreventionor described,isnotthecasewithlegionnaires’disease. controloflegionellosis(includinglegionnaires’disease) setsoutfurtherstatutoryrequirementsfordealingwith 10 Itisimportanttokeeptheincidenceofthedisease thisrisk.Itapplieswheneverwaterisstoredandusedin inperspective.Inrecentyearsupto300casesof awaywhichmaycreateareasonablyforeseeableriskof legionnaires’diseasearereportedeachyearin England legionellosisandinparticulartothefollowingplantand andWaleswhereasthereare180000estimatedcases systemswhenevertheHealthandSafetyatWorketcAct ofpneumoniafromallcauses.Manycasesof 1974applies: legionnaires’diseaseareinpatientswhohaverecently travelledabroad.Infectionswhichoriginateinthis (a) watersystemsincorporatingacoolingtower; 2 PrintedimagedigitisedbytheUniversityofSouthamptonLibraryDigitisationUnit (b) watersystemsincorporatinganevaporative risktheypresentshouldbeassessed.Riskshouldbe condenser; assessednotjustfortheroutineoperationoruseofthe systembutalsoinrelationtobreakdown,abnormal (c) hotwaterservices,exceptwherethevolumeofhot operation,commissioningorunusualcircumstances. waterinthesystemdoesnotexceed300litres; (d) hotandcoldwaterservicesirrespectiveofsizein 21 Theassessmentshouldtakeaccountof: psursecmeipsteibslwe,hesruechocacsuhpeaanlttshacraerepaprrteicmuilsaersly; (a) thepotentialfordropletformation; (b) watertemperature; (e) humidifiersandairwasherswhichcreateaspray ofwaterdropletsandinwhichthewater (c) thelikelyrisktothosewhowillinhalewater temperatureislikelytoexceed20°C; droplets; (f) spabathsandpoolsinwhichwarmwateris (d) meansofpreventingorcontrollingtherisk. deliberatelyagitatedandrecirculated. 22 Dropletsmaybecreatedinvariouswayssuchas 16 Whilethisisnotanexclusivelistitidentifiesthose byspraying,bubblingandimpactwithhardsurfaces. systemsmostlikelytocauseinfection.Otherplantand Largedropsmaybereducedtorespirablesizebyfurther systemscontainingwaterwhichislikelytoexceed20°C impactorevaporation,andthesesmallerparticlesmay andwhichcanreleaseasprayoraerosol(acloudof persistforlongperiodsorbecarriedonaircurrents. waterdropletsand/orparticles)duringoperationorwhen beingmaintainedmayalsopresentarisk. 23 Inassessingriskanddrawingupprecautions particularattentionshouldbepaidtocircumstances 17 TheApprovedCodeofPractice(ACOP)places where: responsibilityonemployersandothersto: (a) thepopulationcontainsahighproportionof (a) identifyandassesssourcesofrisk; susceptiblepeopleas,forexample,inmany (b) prepareaschemeforpreventingorcontrollingthe hospitalsandnursinghomes;or risk; 2(b5) thenumberofpeopleatpotentialriskishighas, (c) implementandmanageprecautions; forexample,indenselypopulatedareas. (d) keeprecordsoftheprecautionsimplemented. 24 Thelistinparagraph15ofthisbookletmaybe 20 assumed,innormalcircumstances,toincludeall 18 TheACOPalsosetsouttheresponsibilitiesof currentlyknownsourceswheretheriskissufficientto manufacturers,importers,suppliersandinstallersof warrantthemeasuresrequiredintheApprovedCodeof productsandservices.ItisenforcedbyHealthand Practice.Thisdoesnotmeanthatthelistincludesall SafetyExecutiveinspectorsinfactories,hospitals, possiblesources,orthatcasesoflegionnaires’disease laboratories,educationestablishments,docksand willbeavoidedbyapplyingprecautionssolelytothe constructionsites.Inshops,offices,warehouses,hotels systemsandplantlisted.Wheneverariskisidentifiedail andcateringestablishmentsitisenforcedbylocal reasonablypracticableprecautionsshouldbeapplied. authoritieswhoalsohaveresponsibilitiesforpublic However,experiencetodateindicatesthattheriskfrom health.Recentoutbreaksoflegionnaires’diseaseinthe plantandsystems,otherthanthoseinparagraph15,will UKhavedemonstratedtheimplicationsforpublichealth. normallybeverysmall. 19 DutiesundertheACOParequalifiedbythe conditionthattheymustbe‘reasonablypracticable’.This DRAWINGUPANDAPPLYINGPRECAUTIONS meansthatboththedegreeofriskandthecostand difficultyofapplyingcontrolmeasuresshouldbe Oncetheriskhasbeenidentifiedandassessed,a accountedforindeterminingwhatmeasuresshouldbe schemeshouldbepreparedforpreventingorcontrolling taken. it.Theprimaryobjectivesshouldbetoavoidconditions whichpermitIegionellatoproliferateandtoavoid IDENTIFICATIONANDASSESSMENTOFRISK crirsekatmiangyabespcroanytroorllaeedrobsyolm.inWihmeirsiengthtisheisreimlperaascetiocfal,the dropletsandbypreventingwaterconditionswhichpermit andwhSiychs-tienmcsorspuosrcaetpetiablpeotteontcioallonmiesaatnisonfobrycireegaitoinnegllaand vIeegriyonleolwlacotnocpernotlrifaetriaotne.sLinegmiaonneyllwaatmearysbyestpermessebnuttibny disseminatingwaterdropletsshouldbeidentifiedandthe carefulcontrolitwillbepreventedfrommultiplying. 3 PrintedimagedigitisedbytheUniversityofSouthamptonLibraryDigitisationUnit 26 Theapplicationofprecautionstospecificsystems manager,directororhavesimilarstatuswithsufficient isdiscussedinlaterparagraphs.Ingeneral,proliferation authoritytoensurethatmeasuresarecarriedout maybeavoidedby: effectively.Staffresponsibilitiesandlinesof communicationmustbeproperlydefinedandclearlyset (a) avoidingwatertemperaturesbetween20°Cand o3u0t.Staffmustbeproperlytrainedandcompetent.The 45°C.Watertemperatureisaparticularlyimportant implementationandeffectivenessoftheprecautions factorinthecontrolofrisk; mustbemonitored,andstaffwitharoletoplayintaking (b) aeovnnocisoduuirrnfagagcweeasttheinercgsotrnaotgwantcahttiowofint.bhioSwftaiatlgemnra()stwliihominecsmhatchyaatnform pdbureteicmeaasudtseiootntoshaamtlulpsortwecfbaoeurtssituoapfnefsrwvahirseoedslt.ielalAviremrpoarlnegameremenetanebtdss.ensthofurlodm harbourlegioneilaandprovidelocalconditionsthat Communicationsandmanagementproceduresare fewaoenbracoltovohuenerg2ra0gpi°eetsCr;iittoesdmgspreoirnwatathu.wraIefrwmiastbmeuorirliedsinaliglkleoolrywietndohrtoiotsestand prpparerresetcpciaoacunuutsltiaiirobolnlnyses.ifmmoFparooyrdritefcaxfhneaatrmenwpngltheeea,rwsephreeescsneptvosesnhsroiiaffblttilwhpieoetroytpkrfleoiearstaaimrpnevepnoltlyvioenrdg,or (c) avoidingtheuseofmaterialsinthesystemthat thepersonwhomonitorstheefficacyofawater canharbourorprovidenutrientforbacteriaand treatmentregimemaynotbethepersonwhoappliesit. otherorganisms; inthesecircumstances,responsibilitiesshouldbewell (d) kuepeopfinsgedtihmeesnytssteetmccwlheiacnhsmoaayshtaorabvoouirdbtahcetebruiialdor dtCoeofmoiumntuesndiidicenawctroiimtoipnnasgnsaihneodsuluadnnddbeecros‘ntfasoiuoll-dtsaabfneyt’.salTlwhhcioosnacmleasroyneabdpe.plies provideanutrientsourceforthem; responsibleforcertainpartsoftheprecautionaryregime. (e) theuseofwatertreatment,forexample,treatment Organisationsshouldsatisfythemselvesofthe chemicals,whereitisappropriateandsafetodo competenceofcontractorsinthisareaofworkbefore so;and gainingtheirassistanceintreating,monitoring,cleaning plantetc. (f) ensuringthatthesystemoperatessafelyand correctlyandiswellmaintained. RECORDKEEPING 27 Indrawingupaschemeforcontrollingrisk, accountshouldbetakenbothoftheriskandthecosts 31 Toensurethatprecautionscontinuetobecarried andpracticaldifficultyofimplementingprecautions.The outandthatadequateinformationisavailablefor variousfactorsthatcontributetotheriskshouldbe checkingwhatisdoneinpractice,arecordshouldbe consideredandanappropriatepackageofmeasures keptshowingtheinformationspecifiedintheApproved preparedandimplemented.Thosemeasureswhich CodeofPractice. Precautionarymeasuresand requirelittleornoexpenditureshouldbeimplemented treatments,monitoringresultsandremedialworkshould immediately;asystemofprioritiesmaybeusedfor beloggedandsignedorinitialledbythepersonwhohas othersplacinggreateststressonthosewatersystems carriedoutthework.Sufficientinformationshouldbe whichpresentgreatestrisk.Forhealthcarepremises recordedtoshowwhatmeasureshavebeentakenand wherepatientsmaybeatparticularrisktheDepartment howtheyhavebeenmonitored. ofHealth’sCodeofPracticeThecontroloflegionellaein healthcarepremisesgivesspecificguidance(see 32 Thedetailedinformationrequiredinthelogwill paragraph140). dependonthetypeandcomplexityofthesystemor waterservicetowhichitappliesandthisisdealtwithin laterparagraphsdealingwithparticularsystems. MANAGEMENTANDTHERESPONSIBILITIESAND COMPETENCEOFPERSONNEL RESPONSIBILITIESOFMANUFACTURERS, 28 Inadequatemanagement,lackoftrainingandpoor IMPORTERS,SUPPLIERSANDINSTALLERS communicationhaveallbeenidentifiedascontributory factorsinoutbreaksoflegionnaires’disease.Itis 33 Manufacturers,suppliersandinstallersofplant thereforeimportantthatthosepeopleinvolvedin andchemicalsshouldensurethattheirproductsdonot assessingriskandapplyingprecautionsarecompetent, contributetotheriskoflegionnaires’diseaseor,where trainedandawareoftheirresponsibilities. thisisimpractical,itshouldbepossibletocontrolthe risk. 29 Onepersonshouldbeappointedasbeing responsibleforoverseeingtheassessmentand 34 Thepreciseresponsibilityofmanufacturersetcwill implementationofprecautions.Thispersonshouldbea dependonthetypeofproduct,theextentoftheirrole PrintedimagedigitisedbytheUniversityofSouthamptonLibraryDigitisationUnit (whethertheyonlysupplytheproductoriftheyinstall watersoftenersandfilters,andoutletsincludingtaps, andcommissionit),theriskitpresentsandlocal showersandotherappliances.Proliferationcanoccur conditions.Eachcasemayneedindividual wheneverconditions,andespeciallytemperatures,are consideration.Someexamplesoftheseresponsibilities idealforgrowth. are: 38 Inpractice,legionellaislikelytoproliferatein (a) themanufacturersofallplantandappliances variouspartsofthesystem,forexample: shouldensurethattheycomplywithwaterbylaws, thattheydonotusematerialswhichsupportthe (a) inwaterstoragetanksandinplantsuchaswater growthofmicro-organismsandthatplantcanbe softeners.Thisismostlikelyifthetanksand readilydrainedandcleaned; associatedplantandpipeworkbecomewarm(if theyareinawarmpartofthebuildingsuchasa (b) thecoolingtowermanufacturershouldensurethat plantroomoraroofspacesubjectedtosolarheat driftisminimised,drifteliminatorsareeffective, gain),iftheyarepoorlyinsulatedandifuseis andtowersaredesignedtobecleanedeasily; intermittent.Theriskfromthissourcewillbesmall ifwaterissubsequentlystoredanddistributedat (c) systeminstallersshouldensurethatthereareno thetemperaturesadvocatedinparagraph50; unnecessary‘dead-legs’andotherareasof stagnation,andthatthesystemcanreadilybe (b) incalorifiers.Theseareamajorsourceof cleanedanddisinfected; proliferationifthecalorifier,orpartsofit,contain waterat20°Cto45°C.Waterinstoragecalorifiers (d) theinstallerorconsultantshouldensurethatthe oftenstratifiessothatalthoughtemperaturesinthe systemisproperlydesigned,installedand bulkofthecalorifiermaybehightherewillbea commissionedandwillworksafely. coolerzonebelowtheheatingcoilswherelegionella canmultiply.Thisisrarelyaproblemifthecalorifier 35 Manufacturersandsuppliersshouldprovide isinconstantuseandtheofftakeissteady. adequateinformationfortheuseroncorrectoperation However,ifuseisintermittent,ortherearesudden andmeansofcontrollingtherisk.Suppliersofproducts increasesindemandsothatthecoolerwateris suchaswatertreatmentchemicalsshouldprovide notheatedforasufficienttime,orifstandby informationontheircorrectandsafeuse,including calorifiersarebroughtintousebeforethewateris conditionsofuse,takingintoaccounttheoperationof adequatelyheatedthroughout,legionellaladen theequipment,waterconditionsandtheircompatibility watermaybedrawnintothedistributionsystem; w3i7thotherchemicalsinthewater. (c) in‘deadlegs’suchasintermittentlyusedwater 36 Whereasupplieralsoprovidesaconsultancy servicesleadingfromthemaincirculatingwater service,asisoftenthecasewithwatertreatment systemtotapsorappliancesandotherpipework companies,careshouldbetakentoensurethatitis connectedtothesystem.Lukewarmwatercan adequateandthatresponsibilitiesandthelinesof standforlongperiodsinpipesserving communicationwiththeuserareclearlysetout.In intermittentlyusedtapsandappliancesand particular,thefrequencyandtimingofservicevisits, legionellamayproliferateinthem. teststobecarriedout,themethodofreportingand actiontobetakenifproblemsaredetected,shouldbe 39 Legionellaisthereforemostlikelytomultiplyin formallyagreedattheoutset.Thelevelofserviceshould calorifierswherewatertemperaturesareinsufficiently bedeterminedbytheneedsofthesystem,notbythe highandinpipeworkleadingtotapsandshowers.Some valueofchemicalsorotherproductssold.Consultants’ largehotwatersystemsdonotincorporateacalorifier visitsshouldbemadewhennecessary,notjustwhen butheatwaterinstantaneouslybeforecirculatingitand convenient,andthereshouldbeaproceduretoensure proliferationmayoccurifwatertemperaturesarebelow thatanyreportssentbypostdonotgoastray. 50°C. 40 Coldwaterservicespresentlittleriskinnormal HOTANDCOLDWATERSERVICES circumstancesalthoughtheremaybesomedangerfrom Therisk tlearmgpeercaoltdurweastecransyesxtceemesdif20u°sCe,isfoirnteexrammitptleen,t,diufweattoerhigh ambienttemperaturesandinadequateinsulation,orif Figure1 showstypicalhotandcoldwaterservices wateristakenfromsourcessuchasboreholes.While inalargebuilding.Legionellamaycolonisestorage theriskisgenerallysmall,itmaybesignificantin tanks,calojifiers,pipeworkandassociatedplantsuchas premiseswhereoccupantsareparticularlysusceptible. 5 PrintedimagedigitisedbytheUniversityofSouthamptonLibraryDigitisationUnit Watersupply lowestpoint Figure1 Hotandcoldwaterservices 6 PrintedimagedigitisedbytheUniversityofSouthamptonLibraryDigitisationUnit Precautions andadrainconnectionshouldbeprovidedatthispoint. 41 Havingassessedtheriskitwillbenecessaryto 46 Pipeworkshouldbeasshortanddirectas determinetheappropriateprecautions.Themain possible,especiallywhereitservesintermittentlyused objectiveistooperatewaterservicesattemperatures tapsandappliances.Theneedforintermittentlyor whichdonotpermitthegrowthoflegionellaandtoavoid infrequentlyusedtapsandappliancesshouldbe stagnation.Itisalsoimportanttoensurethatthesystem reviewed;iftheyarenotnecessarythesupplypipe iscleaninordertominimisetheopportunityforbacterial shouldbecutoffasfarbackaspossibleandremoved. contamination. 47 Ifcalorifiersandpipeworkcannotbedesignedto Selectionofmaterials meetthetemperaturesrequiredinparagraph50,orifthe systemnecessarilyincorporates‘dead-legs’, 42 Certainfittingsandmaterialsusedinthe considerationshouldbegiventoothermeansof constructionofwatersystemsmaysupportbacterialor preventinglegionellafromcolonisingit.Techniques fungalgrowth.Examplesincludeleather,somerubbers, availableinclude: jointingcompoundsandmastics,woodenpackingand certainplastics.Onceanunsuitablefittinghasbecome (a) on-linepasteurisationofcirculatingwaterby coloniseditmaycontinuetoseedthewatersystem.Itis raisingitstemperaturetoalevelatwhich oftendifficulttoidentifysuchfittingswithoutassistance legionellaisrapidlykilled,thencoolingitinaheat fromthewatercompany. Thewaterfittingsand exchangertoasuitablecirculationtemperature; materialsdirectory,publishedbytheWaterResearch and Centre,listsfittingsandmaterialswhichareacceptable underbylawsforconnectiontothemainswatersupply. (b) traceheatingof‘dead-legs’,eithertomaintain Theiraddressis:HenleyRoad,Medmenham,POBox wateratover50°Cinpipeworkortoraiseitto 16,Marlow,BucksSL72HD. highertemperaturestoachievethermal disinfectiononaregular(usuallyweekly)basis. Systemdesignandconstruction 48 Suppliersofpasteurisationortraceheating 43 Watersupplytanksandotherpartsofthe systemsshouldbeaskedtoverifytheirsuitabilityand distributionsystemshouldbewellenclosedtoprevent efficacy.Theperformanceofsometraceheating foreignmatterentering.Tanksshouldbecoveredbylids systemsdesignedtomaintainwaterat50°Cmay withoverlappingedgeswhicharesecuredtothetank. graduallydeteriorateanditisimportantthatthisshould Overflowsshouldbeprotectedbymeshscreens.Tanks notoccurandresultinwaterbeingheldatlower shouldnotbeoversizedand,wheretwoormoretanks temperaturesinthepipework. seenrsvuerethtehastawmaetesryfsltoewms,tihtrsohuoguhldbobtehdteasnkisg.neTdanskosasto 49 Wherepossible,thelayoutofcoldservicesand installedinwarmroofspacesandplantroomsmayneed tanksshouldensurethatwaterdoesnotbecomewarm. tobeinsulated. Forexample,tanksandpipeworkshouldnotbe positionedclosetoheatsourcesorwheretheycouldbe 44 Calorifiersshouldbecapableofheatingtheir affectedbysolargainunlesstheyareeffectively contentstotherequiredtemperaturethroughout.If insulated. stratificationoccursinacalorifiertosuchanextentthat watertemperaturesthroughoutthecalorifierdonot Operation brnoeeatcctehosms6a0orf°yCtthoe(wpchraloeovnriifdtieheerar,emeigesabnnyosadnfroariwmhmeoaefftr)isniitgomnwaayhteebarteeinrtohrea t5h0atprWeavteenrttsheervpircoelsifsehraotuilodnoofpelreagitoenealtlat,emtphaetraist:ures cpaulomripfeiedr.cTirhceuslaetiaornefnrootmitnhteetnodpedtotothoepebroattteomofthe (a) hotwaterstorage(calorifiers),60°C; continuously;theyshouldbetimeroperatedtoheatthe (b) hotwaterdistribution,atleast50°Cattainableat contentsofthecalorifierto60°Cthroughoutforanhour thetapswithinoneminuteofrunning; whenthereisnodrawoff(usuallyatnight). (c) coldwaterstorageanddistribution,20°Corbelow. 45 Tanks,calorifiersandotheritemsofplantshould bbeerpeoasdsiilbyleactcoeisssoilbalteeftohrecmleaannidntg.heIyfnsehcoeuslsdariyn,coirtpsohroautled 5d1angerAtofwastcearldtienmgpwehriacthurienscraebaosvees5wi0t°hCttehmepreeraitsuare. sdeplronaaonitutnhagqcthuoitntchnokeleypyce.tfraiWlmlohinttesortwaheatertpdrohsesemstilohbovelwaeell,sotowpfeipspsoteilnsuptdossgihenwothuailinncddhtbhdaeerraeisinynlsstattarhlegelemed Tcynoeohgnueltniagrgciitsb.cklheAdi.tledHp5roee0wnn°,edCvstethrheb,eovterthihrseyoknrotliotdse,kmmotaposnetadrapftteoeuowtrpheploeeasonewpidllwelit,tbihmepaesretonifcsuolrayrly (toavoidpocketsofwaterwhenthesystemisdrained) loss,willbegreater. PrintedimagedigitisedbytheUniversityofSouthamptonLibraryDigitisationUnit