Overview of Control of Legionella in hot and cold water systems - - PowerPoint PPT Presentation

Health and Safety Executive

Overview of Control of Legionella in hot and cold water systems

Matthew Hamar HSE - Cardiff

What is Legionellosis?

• Collective name for diseases caused by

bacteria legionella.

• Both pneumonia and

non-pneumonia varieties.

• The species Legionella pneumophila

presents the most serious hazard.

• Non pneumonia diseases include pontiac

fever-high strike rate with a legionella

• utbreak

Legionella pneumophila

• This pneumonia is fatal in 10-12% of cases.
• Incubation period 2-10 days (usually 3-6)
• Symptoms include high fever, general malaise,

muscle and joint pains, headache, dry unproductive cough, chest pains and respiratory distress

• Not everyone exposed will develop symptoms
• Some people will not develop the full blown

disease and may experience a mild flu like infection

• Can be treated effectively using antibiotics

Number of cases of Legionellosis by year of onset of symptoms 2005 to 2014 (E&W)

Number of confirmed cases of Legionnaires' disease by month and year of onset, 2013–2015 (E&W)

People at greatest risk

• Old and infirm
• Men more susceptible than women
• Over 45 years of age
• Smokers
• Alcoholics
• Diabetics
• Existing respiratory problems
• Immuno-suppressed people

Infection route

• Inhalation of contaminated water

droplets containing the viable bacteria

• Water droplets less than 5 microns
• No person to person transmission
• Not contracted by drinking

contaminated water

Where is legionella found?

• Legionella is widespread in both natural water

sources and artificial water systems.

• It multiplies:
• where temperatures are between 20-450C;
• where nutrients are available; and
• where water is stagnant or re-circulates.
• Infection can then occur by the inhalation of

aerosols or particles generated from the source.

Barrow-in-Furness outbreak

• 2500 people affected
• 494 clinically diagnosed

cases

• 180 confirmed
• 7 deaths

Legionnaires at Care Home

L8- Legionnaires` disease

Foreseeable and Preventable

L8 ACOP describes the responsibilities

• f employers
• Identify and assess risks of legionellosis;
• avoid the use of systems that give rise to a

foreseeable risk of legionellosis or, where this is not reasonably practicable, prepare a written scheme for minimising the risk from exposure;

• implement and manage the scheme of

precautions including the appointment of a person, or persons, to take managerial responsibility and to provide supervision; and

• keep appropriate records.

Risk Assessment should include:

• the management responsibilities and name of

the responsible person;

• an assessment & comprehensive schematic

(where complex) of the system;

• details of precautions taken including:
• the control method/s – inspection / monitoring

and maintenance programme (eg checking the system is kept clean;

• records of operation, monitoring and remedial

work;

• population exposed and risk

Example of a good schematic

Methods of control of legionella in hot and cold water systems

• temperature regime;
• biocide treatments;
• ionisation treatment;
• ozone; and
• UV treatments

Temperature parameters

20 0C bacteria remains dormant but viable Bacteria 45 0 C 50 0 C -90% killed in 2 hours 600C -90% killed in 2 minutes 700C- rapid kill to 100% Avoid temperatures in range 20-50 degrees Celsius

Overview

• f Temp

controls

Store cold water at <200C Distribute cold water at <200C Store hot water >=600C distribute hot water at >=500C Return water >=500C Note – Hot water should achieve 500C within 1 minute & cold should achieve less than 200C within 2 minutes at sentinel outlets

Sentinel Outlets

the nearest and furthest/last outlets from hot and cold water cylinders and tanks.

Dead end and dead legs need to be removed

• A dead end- a redundant length of pipe, closed at one end,

through which no water is flowing

• A dead leg - is a pipe leading to an outlet which water flows

but the outlet is un-used or infrequently used. All need to be removed by cutting them back to the main pipe run

Thermostat mixing valves

• Picture TMVs

these blend hot and cold water to reduce the temperature where a scald risk is present

Expansion vessels in hot or cold water systems (not central heating)

• Preferably be flow through

design

• Have a drain valve

– flush through and purge to drain (HSG274 Pt2 Table 2.1)

• Minimise volume stored
• Should be sited

– in cool areas – vertically on pipework not horizontally

Specialised Assisted Baths

• Separate cleaning

shower head system

• Hydro-massage

function

• Flexible hoses
• Expansion vessels
• Filters

Other issues to address:

• TMVs should be fitted as close as possible to the point of

use (typically one per outlet);

• Infrequently used outlets should be flushed weekly (includes

short usage and no hot water flowing);

• Shower heads and hoses should be dismantled, cleaned and

descaled or replaced at least quarterly.

• Redundant supply pipework should be cut back as far as

possible to a common supply;

• Replace EPDM (ethylene propylene diene monomer). rubber

hoses with eg. PE (polyethylene), PEX (cross-linked polyethylene

• Keep water system clean

Monitoring water temperatures for legionella control

Measure the temperature at the hot water tanks monthly

• hold the surface probe against the pipe

work at the hot water tank outlet

• check the temperature tallies with any

fixed thermometer, if installed.

Measure the temperatures at the sentinel cold water and hot water outlets monthly

Use the immersion probe to measure the temperature of the water flowing from the outlet (NB – on hot outlet where TMV is fitted, this needs to be done on TMV inlet pipe)

• Hot water should measure at least

500C within 1 minute of running water

• Cold water should measure

less than 200C within 2 minutes

Measure sentinel hot water temperature at inlet to TMV monthly

Measure at least 500C within 1 minute of running water

Measure the temperatures at the cold water tanks 6 monthly

Incoming water Water in tank Measure less than 200C

Common failings 1

• No Legionella risk assessment and occupiers are ignorant
• f the control and monitoring requirements (lack of

competence)

• Assessment findings not being implemented
• No schematics or not comprehensive
• Sentinel outlets not identified
• Not measuring hot water temperatures at inlet to TMVs

where fitted

• Homes only measure and record hot water temps after

tmv’s for scald risk

• Tmv’s fitted too far from outlet
• Not measuring hot water storage temperatures
• Hot water storage thermostats set below 50 degrees C

Common failings 2

• No temperature gauges fitted to hot water outlets and

returns (and no one measuring with surface probe)

• Hot water vent pipe overflowing to cold water tank
• Cold water stored above 200C (eg un-insulated cold water

tanks located on roofs)

• Cold water tank lids not tight fitting or broken
• Insects screens not fitted to cold water over flows and

vents

• Dead legs / ends present
• Infrequently used outlets not flushed weekly
• No cleaning of shower heads
• Evidence that some Water treatment company reports do

not reflect the inadequate management, treatment and control of legionella at the homes

When is legionella sampling required?

• Where storage and distribution

temperatures are reduced from those required

• Where an outbreak is suspected or

identified

• Where assessment identifies it is

necessary to help monitor effectiveness of controls

When is disinfection needed?

• If required temperatures not being

achieved

• System has been substantially altered; or
• During or following an outbreak

Other issues to consider

What is an infrequently used outlet? What is the impact of green technologies or energy conservation on Legionella control? How many people are contracting Legionnaires disease from care homes? RIDDOR does not require non-worker reports of disease to HSE – but requirement to report to HPA

Frequency of Monitoring Temperatures

Measure the temperature at the hot and cold water sentinel outlets and the hot water tank Six monthly Check the temperature at the cold water storage tank/s (at least once in winter and once in summer during a hot period); Annually Check a representative number of cold water outlets on a rotational basis

Frequency of water temperature checks

The Frequency of Other Checks

At least weekly Flush infrequently used hot and cold water outlets At least 3 monthly Clean and de-scale or replace shower heads and hoses At least annually Visually inspect the cold water storage tank/s and clean and disinfect as required Check the schematic diagram/s of the H &CW system to ensure they are correct and up to date (eg addition or removal of water tanks and outlets)

Note: All checks should be carried out using safe systems and some checks or corrective actions may need to be done by an external competent person

Frequency of other checks

Further information

HSE H&SC Legionella webpage: http://www.hse.gov.uk/healthservices/legionella.htm HSE Legionella H&CWS webpage: http://www.hse.gov.uk/legionnaires/hot-and-cold.htm HSE SIM – Control of Legionella in H&CWS http://www.hse.gov.uk/foi/internalops/sims/pub_serv/07-12-07/index.htm HSE ACOP L8: http://books.hse.gov.uk/hse/public/saleproduct.jsf?catalogueCode=9780 717617722 HSE ACOP HSG274 Part 2 http://www.hse.gov.uk/pubns/priced/hsg274part2.pdf HSE Safety Notice: http://www.hse.gov.uk/safetybulletins/legionella2.htm

Schematics