Legionella E-news -- 20 February 2002

home

back to Legionella Enews archives list

**IN THIS ISSUE**

1. Water Hammer Arrestors Versus Air Chambers

2. Legionella Prevention Training Course

*******************************************************************

1. WATER HAMMER ARRESTORS VERSUS AIR CHAMBERS

Excerpted from Management Plan for Legionella and Other Waterborne

Pathogens (http://hcinfo.com/managementplan.htm), by Matthew R. Freije

*******************************************************************

Water hammer, the banging sound you sometimes hear when you quickly

shut off a faucet, is controlled by either air chambers or water hammer

arrestors (also called shock absorbers).

One hospital found high legionellae counts in water hammer arrestors.

After removing the water hammer arrestors, the percentage of water

outlets testing positive for Legionella dropped significantly, and no

new cases of legionellosis were identified (Memish, Z. A., C. Oxley, J.

Contant, and G. E. Garber. "Shock Absorbers as a Source of Legionella

pneumophila." Presented at the 4th International Symposium on

Legionella, 1992. In: Barbaree, J. M., R. F. Breiman, and A. P. DuFour,

eds. Legionella: Current Status and Emerging Perspectives. Washington,

D.C.: American Society for Microbiology, 1993; 261-262).

Air chambers, however, which will normally be required if water hammer

arrestors are not used, may be even more conducive to Legionella growth

than are arrestors, because air chambers become waterlogged and harbor

stagnant water.

Water hammer arrestors hold less water than air chambers because they

have membranes that separate the water from the air. In some types of

water hammer arrestors the membranes are diaphragms -- a dome shaped

sheet of rubber or stainless steel that's fixed at the sides of the

tube but flexible in the middle so that it moves up and down with

variations of water pressure, somewhat like a trampoline. Other

arrestors have piston-type membranes made of either plastic or brass.

Studies have not been undertaken to compare water hammer arrestors with

air chambers with respect to legionellae growth, or one type of water

hammer arrestor with another type, so there is no data on which to base

decisions. However, it would seem that two Legionella-prevention

factors should be considered in comparing one type of arrestor with

another: (1) the amount of water it contains, and (2) whether the

components are made of rubber, stainless steel, or brass. The less

water the arrestor holds, the better. In most cases piston type

arrestors will hold less water than will the diaphragm types, but there

may be exceptions with various models. Components made of stainless

steel or brass will be less conducive to Legionella growth than will

components made of rubber or plastic.

Therefore, for future plumbing renovations, consider water hammer

arrestors with piston-type membranes until better technology becomes

available to control water hammer. If using a diaphragm type arrestor,

prefer a model with a stainless steel diaphragm instead of one with a

rubber diaphragm.

*******************************************************************

2. LEGIONELLA PREVENTION TRAINING COURSE

*******************************************************************

Montreal -- March 7-8, 2002 (Thurs.-Fri.), at the Holiday Inn Select

Montreal Centre-Ville, a 4-star hotel located in the heart of downtown

Montreal.

New York City -- March 21-22, 2002 (Thurs.-Fri.), at the Wyndham Garden

Hotel LaGuardia Airport.

Chicago -- May 1-2, 2002 (Wed.-Thurs.), at the Doubletree Hotel O'Hare

Airport-Rosemont, an upscale hotel located 1 mile from O'Hare

International Airport.

To register for the seminars, or get more information, visit

http://hcinfo.com/legionellaseminar.htm or e-mail hcinfo@hcinfo.com.

*******************************************************************

Please mention Legionella E-news in listservs or on your web site.

Sample announcement: "Legionella E-news is a free monthly e-newsletter

that covers recent outbreaks, new publications, and new technology. To

subscribe, go to http://hcinfo.com, or send a message to

hcinfo@hcinfo.com with LEGIONELLA:ADD on the subject line."

*******************************************************************

If you have suggestions, information to offer, or complaints, please

send a message to hcinfo@hcinfo.com. We appreciate feedback!

*******************************************************************

You have permission to send this newsletter to others, post it on your

web site, or include it in listserv posts, under the strict condition

that you include the following notice to properly credit the source:

"Excerpted from Legionella E-news, a free e-newsletter available at

http://hcinfo.com."

THANK YOU!

Matt Freije

HC Information Resources Inc.

http://hcinfo.com