1. 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
Risk assessment should include:
Responsibilities of competent person
An assessment of the system present. Consideration of boiler type / method of heating etc. & detailed schematic drawing
Identification and implementation of control measures
Remedial action to further reduce risk e.g. removal of deadlegs / fitting of insect screens / raising of hot storage temps if required.
Record keeping – this will need to show monitoring is in place, correct temperatures are maintained and that any departure from this is identified and remedied within reasonable time period.

2. Example of a good schematic
Good example of a schematic
Enables sentinels to be identified and where outlets are supplied from.
NB complex system owing to large number of cold water tanks and calorifiers.

3. Methods of control of legionella in hot and cold water systems
temperature regime;
biocide treatments;
ionisation treatment;
ozone; and
UV treatments
This presentation concentrates on temperature control – however, there are other methods of control that can be used.
These can be used in addition to temperature
[See developments on copper / silver ionisation]

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

5. H&CW System
Simplified view of hot and cold water storage system with circulating hot loop.
Storage of both hot and cold water are the most ‘at risk’ systems in H&SC sector as they require controls to ensure that storage and pipework remains clean and temperatures are maintained

6. Overview of Temp controls
Distribute cold water at <200C
Store cold water
at <200C
Note – Hot water should achieve 500C within 1 minute & cold should achieve less than 200C within 2 minutes at sentinel outlets
Store hot
water
>=600C
Temperatures to be achieved:
Cold Water and storage and supply
Storage should be less than 20 dgrees C
Outlets should be less than 20 dgrees C
Hot Water storage and supply
Storage should be greater than 60 degrees C
Supply to outlets & distribution should be greater than 50 degrees C
NB vent pipe from calorifier should ideally not discharge into cold water tank. If it does systems to identify any discharge should be considered. Easier to carry out remedial action to discharge to a safer point.
Case
Scalding of baby following discharge from vent pipe into plastic cold water store.
Return
water
>=500C
distribute hot
water at >=500C

7. The incoming and storage temperature of the cold water <200C.
COLD WATER TANK
The incoming and storage
temperature of the cold water <200C.
The tank should be:
- sized to supply one day’s water usage;
-should be sited in a cool place;
-should be thermally insulated to protect
from extremes of heat; and
-should possess a tight fitting lid and a vent.
The water over flow pipe and vent should
be fitted with an insect screen;
The water surface should be
clean and free of any debris or contamination;
over
flow

8. The hot water cylinder should:
- be sized to provide water needed
for a day’s usage;
be insulated;
deliver outgoing water at a
temperature of at least 600C and return
water of at least 500C
-be fitted with a drain valve
The vent pipe should preferably not
drain to the cold water tank.
Large cylinders should be fitted with a
shunt pump to mix the water and heat
the whole volume to at least 600C
for at least one hour each day

9. Water distribution : Hot water should reach at least 500C
within 1 minute of running outlet;
Cold water should be less than 200C
within 2 minutes of running outlet;
Temperatures should be measured
monthly at the sentinel outlets
(where TMVs are fitted the
temperature of the pipe work at the
inlet to the TMVs should be
measured eg using a surface probe
thermometer)