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Are you closing your premises for the Christmas break? We suggested some steps to reduce the risk of Legionella bacteria being a problem when you reopen.
As many business will close for a period of time over Christmas which could be well over a week. The Christmas period is a much needed break for everyone and when you leave work, you don't want to have to think about it until you return after Christmas.
What you need to know
When closing a premises many people may think that it's 'lights out and lock the doors' and all will be well however in my industry we look at the water hygiene aspect and how long periods of buildings be unoccupied has an affect on the quality of the water. There are three main things that really encourage Legionella bacteria:
Stagnation (water that doesn't move)
Nutrient (food source for bacteria i.e. scale)
Warm water
These 3 elements do not all need to be present for Legionella bacteria to cause a problem so if only one existed, the bacteria can still thrive.
Prior to closing consideration should be given to the suggested actions below:
can the cold water storage tank be bypassed and the tank drained down?
if the tank cannot be isolated, can the tank be treated in any way, such as with sodium hypochlorite or other suitable biocide. Adding a biocide, on a regular basis (weekly) manually, to down cold water service tanks will help reduce bacteria and legionella growth.
if cold water services are subject to heat gain from warm risers; or are close to LTHW or HWS systems, turn off the heating systems; open up the riser cupboard doors and leave them open, if safe to do so.
turn off LTHW systems; all calorifiers and hot water cylinders in landlords and tenants areas. The HWS circulating pumps should be kept running.
point of use heaters, in landlord and tenants areas, notably those beneath sinks should be switched off locally as they heat the cupboards they are stored in and the cold water pipework.
drinking water coolers should be switched off.
if allowed access to the premises flush sentinel points weekly for 5 minutes. Sentinel outlets for most premises are the top and bottom of each mains; hot water and down cold water service riser.
Reopening
If water systems have not been flushed and maintained;
prior to reoccupation, drain down all stored water services (tanks and calorifiers) and refill. Turn on all water heaters to 70oC and undertake thermal disinfection flushing all hot water outlets. Return all thermostats to 60oC Undertake extensive flushing of all cold water outlets, including all outlets in kitchens; and toilet areas. Flush all toilets several times. Ideally the building should be disinfected. However, priority should be given to premises where there has been no flushing.
As soon as possible after reinstatement of water services, sampling should be undertaken as soon as possible to ensure the water systems are safe.
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