SIST-TP CEN/TR 16355:2012

Recommendations for prevention of Legionella growth in installations inside buildings conveying water for human consumption

This Technical Report provides basic information about the conditions for Legionella growth in drinking water installations in accordance with EN 806 series up to draw-off points and gives recommendations for preventing the growth of Legionella in these installations.

Empfehlungen zur Verhinderung des Legionellenwachstums in Trinkwasser-Installationen

In diesem Technischen Bericht sind grundlegende Informationen über die Bedingungen für das Legionellenwachstum in Trinkwasser-Installationen nach der Reihe EN 806 bis zu den Entnahmestellen und Empfehlungen zur Verhinderung des Legionellenwachstums in diesen Installationen enthalten.
ANMERKUNG 1   Zur weiteren Information siehe Anhang A.
ANMERKUNG 2   Nationale Dokumente hinsichtlich der Verhinderung des Legionellenwachstums sind in Anhang B aufgeführt.

Recommandations de prévention du développement des légionnelles dans les installations de distribution d’eau destinée à la consommation humaine à l’intérieur des bâtiments

Priporočila za preprečevanje razmnoževanja legionele v napeljavah stavb, po katerih teče pitna voda

To tehnično poročilo navaja osnovne informacije o pogojih za razmnoževanje legionele v napeljavi za pitno vodo v skladu s skupino standardov EN 806 do izpustnih točk in navaja priporočila za preprečevanje razmnoževanja legionele v teh napeljavah.

General Information

• Status: Published
• Publication Date: 15-Jul-2012
• ICS: 13.060.20 - Drinking water
• ICS: 91.140.60 - Water supply systems
• Technical Committee: IOVO - Water supply and waste water engineering
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 04-Jul-2012
• Due Date: 08-Sep-2012
• Completion Date: 16-Jul-2012
• Ref Project: CEN/TR 16355:2012 - Recommendations for prevention of Legionella growth in installations inside buildings conveying water for human consumption

Standards Content (Sample)

SLOVENSKI STANDARD
SIST-TP CEN/TR 16355:2012
01-september-2012
3ULSRURþLOD]DSUHSUHþHYDQMHUD]PQRåHYDQMDOHJLRQHOHYQDSHOMDYDKVWDYESR
NDWHULKWHþHSLWQDYRGD

Recommendations for prevention of Legionella growth in installations inside buildings

conveying water for human consumption
Empfehlungen zur Verhinderung des Legionellenwachstums in Trinkwasser-
Installationen
Recommandations de prévention du développement des légionnelles dans les

installations de distribution d’eau destinée à la consommation humaine à l’intérieur des

bâtiments
Ta slovenski standard je istoveten z: CEN/TR 16355:2012
ICS:
13.060.20 Pitna voda Drinking water
91.140.60 Sistemi za oskrbo z vodo Water supply systems
SIST-TP CEN/TR 16355:2012 en,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TP CEN/TR 16355:2012
TECHNICAL REPORT
CEN/TR 16355
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
June 2012
ICS 91.140.60
English Version
Recommendations for prevention of Legionella growth in
installations inside buildings conveying water for human
consumption

Recommandations de prévention du développement des Empfehlungen zur Verhinderung des

légionnelles dans les installations de distribution d'eau Legionellenwachstums in Trinkwasser-Installationen

destinée à la consommation humaine à l'intérieur des
bâtiments

This Technical Report was approved by CEN on 25 March 2012. It has been drawn up by the Technical Committee CEN/TC 164.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,

Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 16355:2012: E

worldwide for CEN national Members.
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Contents Page

Foreword ..............................................................................................................................................................3

1 Scope ......................................................................................................................................................4

2 Normative references ............................................................................................................................4

3 Terms and definitions ...........................................................................................................................4

4 General recommendations ...................................................................................................................4

4.1 Conditions for Legionella growth ........................................................................................................4

4.2 Temperature ...........................................................................................................................................4

4.2.1 General ....................................................................................................................................................4

4.2.2 Cold water temperature .........................................................................................................................5

4.2.3 Hot water temperature ...........................................................................................................................5

4.2.4 External influences on temperature.....................................................................................................5

4.2.5 Thermal disinfection ..............................................................................................................................6

4.3 Stagnation ..............................................................................................................................................6

4.4 Biofilm and sediments ..........................................................................................................................6

4.4.1 Biofilm .....................................................................................................................................................6

4.4.2 Sediment .................................................................................................................................................7

5 Types of hot water installation — Legionella prevention recommendations ..................................7

6 Blended water systems within the temperature ranges of 37 °C to 45 °C .......................................9

Annex A (informative) Background ................................................................................................................ 10

Annex B (informative) List of official national documents concerning Legionella prevention................ 11

Annex C (normative) Figures for Table 2 "Types of hot water installation" .............................................. 14

Annex D (informative) Further recommendations for dealing with external influences on

temperature ......................................................................................................................................... 18

Bibliography ..................................................................................................................................................... 23

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Foreword

This document (CEN/TR 16355:2012) has been prepared by Technical Committee CEN/TC 164 “Water

Supply”, the secretariat of which is held by AFNOR.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.

This Technical Report should be read in conjunction with national regulations.

The status of this document as CEN Technical Report has been chosen because most of its content is not

completely in line with practice and regulations in each Member State. This document gives recommendations

for good practice concerning the prevention of Legionella growth in drinking water installations but existing

national regulations remain in force.

In this report, one item of the technical concept to prevent proliferation of Legionella in drinking water

installations is to keep the water temperature out of the range where Legionella can grow and to make the

provision for thermal disinfection.
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1 Scope

This Technical Report provides basic information about the conditions for Legionella growth in drinking water

installations in accordance with EN 806 series up to draw-off points and gives recommendations for

preventing the growth of Legionella in these installations.
NOTE 1 For further information, cf. Annex A.

NOTE 2 National documents regarding the prevention of Legionella growth are shown in Annex B.

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated references,

the latest edition of the referenced document (including any amendments) applies.

EN 806-1:2000, Specifications for installations inside buildings conveying water for human consumption 

Part 1: General
3 Terms and definitions

For the purposes of this document, the terms and definitions in EN 806-1:2000 and the following apply.

3.1
redundant pipe (dead end)

part of a drinking water installation which is permanently not in use but full of water

3.2
cut-off end
remaining part of a redundant pipe after being cut off
4 General recommendations
4.1 Conditions for Legionella growth
The following conditions encourage legionella growth:
 water temperature between 25 °C and 50 °C;
 stagnation of the water;

 nutrients, biofilm and sediment within the installation including water heaters, etc.

4.2 Temperature
4.2.1 General

To restrict the growth of Legionella bacteria the water temperature shall be in a range that the bacteria will not

grow or have minimum growth, wherever possible.
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4.2.2 Cold water temperature

The cold water temperature in the installation should be kept below or equal to 25 °C.

NOTE In some countries or in the summer season it is possible that temperature of the water in the installation will be

above 25 °C and in these cases other solutions should be found to restrict Legionella growth (e.g. flushing, disinfection).

External influences on temperatures are described in 4.2.4.
4.2.3 Hot water temperature

For a drinking water installation without hot water circulation (see Annex C, Figures C.1 and C.3), the water

should be capable of reaching a temperature of minimum 55 °C at any point during normal use.

For a drinking water installation with circulation of hot water, the water in any circulation loop should be

minimum of 55 °C (see Figure 1). Within 30 s after fully opening a draw off fitting the water temperature should

not be less than 60 °C unless otherwise specified by local or national regulations (see EN 806-2).

Key
1 After 30 s not less than 60 °C
2 Not less than 55 °C
Figure 1 — Drinking water installation with circulation of hot water

High hot water temperatures will increase the risk of scalding. Appropriate measures should be taken to

reduce this risk, e.g. notices by hot water draw-offs or mechanical devices (see Table 1).

Table 1 — Guide values for the risk of scalding in relation to hot water temperature and time of

exposure
Hot water temperature 70 °C 60 °C 50 °C
Time of exposure for
– children < 1 s 3 s 120 s
– adults 1 s 7 s 510 s
4.2.4 External influences on temperature

Ambient conditions can cause problems in maintaining the cold and hot water temperature limits (conduction,

convection and radiation).

To minimise the cooling of the water in a hot water circulation system (pipes with continuous flow), it should be

insulated (see Directive 2002/91/EC [8]).
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To minimise the warming-up of the water in cold water pipes and the slow cooling in hot water pipes other

than being part of a circulation system (e.g. dead-legs, floor service pipes, rising pipes), these pipes should

not be insulated.

NOTE It should be taken into account that all measures of insulation of cold water pipes have only a delaying effect

on the warming up of the cold water but have no influence on the end temperature after warming-up.

Cold water pipes and dead-legs of hot water pipes other than being part of a circulation system should not be

placed in rooms, places or constructions with a temperature above 25 ˚C and should be kept away from heat

radiation sources or places where the temperature at certain times can be higher than 25 ˚C (e.g. below a

glass dome, in technical rooms and cabinets/metering boxes with heating sources). In case of floor heating

systems potable water pipes should not be placed in ceilings or in floors unless adequately insulated.

Further recommendations for dealing with external influences on temperature are given in Annex D.

4.2.5 Thermal disinfection

Hot water systems should have the facility to enable the temperature at any point of the system to be raised to

70 °C for disinfections purposes (see EN 806-2).

NOTE There are several methods for disinfection of a drinking water installation. In this Technical Report, only the

thermal disinfection is mentioned.
4.3 Stagnation

The drinking water installation should be designed and installed in a way that stagnation of the water under

normal use is avoided.

In order to avoid long periods of stagnation the water in every part of the drinking water installation should be

used or flushed at least weekly.

Cut-off ends should be as short as possible, but should be no longer than two times of the internal diameter of

the pipe.

Redundant pipes (dead-ends) should be removed or disconnected, and converted to a cut off end.

Infrequently used pipes should be isolated by a shut-off device or flushed regularly. The length of pipe

between the branch and the shut-off device in the infrequently used pipe should be as short as possible, but

not greater than 150 mm.

NOTE It is understood that in stagnant water Legionella can grow in volumes smaller than 3 l. Therefore, it is

recommended to keep the volume of water contained in the pipework between the circulation system and the draw-off tap

as small as possible. Cf. national or local requirements.
4.4 Biofilm and sediments
4.4.1 Biofilm

Any surface in natural aquatic environments will acquire a biofilm. Biofilm formation generally follows the same

sequence of steps wherever it occurs: formation of a conditioning layer of organic molecules, initial attachment

of bacteria, growth of adhered bacteria resulting in the formation of microcolonies and subsequently a mature

biofilm.

Microorganisms like protozoa often become incorporated within the biofilm and during a certain period

invertebrate larvae and algal spores can settle and grow. Bacterial extracellular polymeric substances (EPS)

constitute the biofilm matrix in which also the organisms like Legionella are embedded.

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For prevention of Legionella growth one should take measurements to minimise the formation of biofilm in

drinking water installations. The potential of biofilm formation is influenced by several aspects, e.g. by

temperature, water treatment, the materials of products in contact with drinking water, the volume flow and

stagnation times. The biofilm potential of materials is therefore an important aspect to monitor (‘unified biofilm

approach’).

NOTE At this point in time the research on biofilm formation is ongoing in order to find out how to define the extent of

biofilm growth and when which actions are to be taken to minimise the growth.
4.4.2 Sediment

Sediment can support the growth of Legionella bacteria and it should be removed on a regular basis from e.g.

storage systems, water heaters, non-flown through expansion vessels (e.g. once a year). Sediment in pipe

work should be avoided by close attention to design parameters in EN 806-2 and EN 806-3.

5 Types of hot water installation — Legionella prevention recommendations

When using thermostatic mixing valves, they should be in accordance with EN 1111 or EN 1287.

When using an inline hot water tempering valve, it should be in accordance with EN 15092.

NOTE Types of hot water installation and relevant recommendations for Legionella prevention are given in Table 2.

All symbols used for the figures in Annex C are in accordance with EN 806-1.
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Table 2 — Types of hot water installation
Hot and cold water separately Mixed hot and cold water
No storage Storage No storage Storage No storage
upstream of mixing upstream of mixing upstream of mixing
valves valves valves
No With No With No With No With No With

circulation circulation circulation circulation circulation circulation circulation circulation circulation circulation

of hot of hot of hot of hot of hot water of hot of mixed of mixed of mixed of mixed

water water water water water water water water water
Figure
C.1 C.2 C.3 C.4 C.5 C.6 C.7 C.8 C.9 C.10
in Annex C
e e e
Tempe
...