Health and safety : the control of legionellosis: proposed regulations requiring the registration of wet cooling towers and evaporative condensers [consultation paper]

23 Pages·1991·1.1 MB·English

by  Great Britain. Health and Safety Executive

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:[phone]Telex:54556
HealthandSafetyExecutive
LibraryandinformationServices
BaynardsHouse
1 ChepstowPlace
WestbourneGrove
LONDONW24TF
Tel:[phone]Telex: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
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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
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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
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(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
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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
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(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
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Watersupply
lowestpoint
Figure1 Hotandcoldwaterservices
6
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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.
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