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Legionella E-news -- 9 January 2003**IN
THIS ISSUE** ================================================================== ==================================================================
2.
PROCEDURE FOR CLEANING HOT WATER TANKS The
following procedure, excerpted from Management Plan for Legionella and
Other Waterborne Pathogens (http://hcinfo.com/managementplan.htm), is
based on recommendations made by a professional tank cleaning company
(this procedure is not appropriate for all tanks): a.
Drain the tank.
b.
Add 2 gallons (7.57 liters) of sodium hypochlorite (12% liquid
chlorine solution that is available from pool supply stores) for every
1000 gallons (3,785 liters) of tank capacity in order to reach 200 ppm
chlorine in the tank when it is filled. Leave the tank filled with
the 200 ppm chlorine solution for at least 3 hours.
c.
Drain the tank again and clean it thoroughly. Flush out sediment.
If feasible, spray with high-pressure steam or water to remove scale and
to more thoroughly remove particles (be sure that the tank lining can
tolerate high pressure spray).
d.
After the tank is thoroughly cleaned, add 1 gallon (3.79 liters)
of sodium hypochlorite (liquid chlorine) for every 1000 gallons (3,785
liters) of tank capacity in order to reach 100 ppm chlorine in the tank
when it is filled. Leave the tank filled with the 100 ppm chlorine
solution for 24 hours. If the tank cannot be taken offline for 24 hours,
then use 2 gallons of chlorine for every 1,000 of water to achieve a
concentration of 200 ppm, and leave the tank filled with the chlorinated
water for four hours. 200 ppm for four hours is not as effective as 100
ppm for 24 hours, particularly for Legionella disinfection, so leave the
solution in the tank for the full 24 hours if possible. In fact, it's
best to leave the solution in the tank for 48 hours; however, if the
tank is made of iron, do not leave the solution for longer than 24 hours
to avoid rusting.
e.
Flush the tank until all excess chlorine is removed. It
has been reported that maintenance workers in Japan contracted
Legionella infections after cleaning the interior of a hot water tank.
Japanese guidelines therefore recommend against physical cleaning of
tanks with high-pressure water or by other means prior to chemical
disinfection, which is why the above procedure calls for chlorination
before as well as after the physical cleaning. The use of high
efficiency respirators may add protection. ================================================================== Go
to http://www.hcinfo.com/legionella1daycourse.htm for more information.
A comparison of our one-day and two-day courses is posted at http://www.hcinfo.com/legionellaseminar.htm. If
you have access to a meeting facility and would like to host a course,
or if you would like private training for your organization, contact
Matt Freije at 760-494-3063 or mf@hcinfo.com. ==================================================================
******************************************************************* THANK
YOU! Matt
Freije, Editor |