Identifying Cooling System Dead Legs Helps Solve Persistent Positive Legionella Test Results

GoalEliminate Legionella risk by improving system design and microbiological control.

<p><!-- wp:acf/two-cols-text {"name":"acf/two-cols-text","data":{"option_change_padding_block":"1","_option_change_padding_block":"field_6629e1de35327","padding_options":"py-to-60","_padding_options":"field_6629e0d2860af","background_colour":"blue","_background_colour":"field_6629e20935328","block_options_clone":"","_block_options_clone":"field_662a1b96b768f","block_title":"Overview","_block_title":"field_6629f36ac5d6b","block_content_clone":"","_block_content_clone":"field_662a1b96b76fb","text_list_0_text_item":"\u003cul class=\u0022list-check-mark\u0022\u003e\r\n \t\u003cli\u003e\u003cb\u003eIndustry: \u003c/b\u003e500 Room Hotel\u003c/li\u003e\r\n\u003c/ul\u003e\r\n\u0026nbsp;","_text_list_0_text_item":"field_662a1bf77d245","text_list_1_text_item":"\u003cul class=\u0022list-check-mark\u0022\u003e\r\n \t\u003cli\u003e\u003cb\u003eApp\u003c/b\u003e\u003cb\u003ei\u003c/b\u003e\u003cb\u003elcation\u003c/b\u003e\u003cb\u003e: \u003c/b\u003eHVAC Cooling Tower System\u003c/li\u003e\r\n\u003c/ul\u003e","_text_list_1_text_item":"field_662a1bf77d245","text_list_2_text_item":"\u003cul class=\u0022list-check-mark\u0022\u003e\r\n \t\u003cli\u003e\u003cb\u003eProblem: \u003c/b\u003ePersistent positive Legionella counts in the cooling tower system despite repeated cleanings and chlorine disinfections\u003c/li\u003e\r\n\u003c/ul\u003e","_text_list_2_text_item":"field_662a1bf77d245","text_list_3_text_item":"\u003cul class=\u0022list-check-mark\u0022\u003e\r\n \t\u003cli\u003e\u003cb\u003eSolution\u003c/b\u003e: A survey identified significant dead legs in the cooling system piping which were subsequently drained, cleaned, and disinfected\u003c/li\u003e\r\n\u003c/ul\u003e","_text_list_3_text_item":"field_662a1bf77d245","text_list_4_text_item":"\u003cul class=\u0022list-check-mark\u0022\u003e\r\n \t\u003cli\u003e\u003cb\u003eResult: \u003c/b\u003eSubsequent Legionella test result for the system was negative\u003c/li\u003e\r\n\u003c/ul\u003e","_text_list_4_text_item":"field_662a1bf77d245","text_list":5,"_text_list":"field_662a1bb97d244"},"mode":"edit"} /--><!-- wp:heading {"level":5} --></p> <h5 class="wp-block-heading">Customer Challenge</h5> <p><!-- /wp:heading --><!-- wp:paragraph --></p> <p>Routine culture testing of the cooling tower system showed&nbsp; a high level of Legionella bacteria. Despite repeated attempts at remediation, the positive Legionella counts could not be completely resolved by the standard cleaning and chlorine disinfection protocols.&nbsp;</p> <p><!-- /wp:paragraph --><!-- wp:image {"id":7014,"sizeSlug":"full","linkDestination":"none","align":"center"} --><!-- /wp:image --></p> <p><img style="display: block; margin-left: auto; margin-right: auto;" src="/link/843ae869890b427da0b567a3cb3e3a46.aspx" alt="" width="700" height="265" /></p> <p><!-- wp:heading {"level":5} --></p> <h5 class="wp-block-heading">Recommended Solution</h5> <p><!-- /wp:heading --><!-- wp:paragraph --></p> <p>A comprehensive survey by Chem-Aqua identified dead legs resulting from the terminated piping left in place when a chiller was removed from service years earlier. Dead legs are sections of a water system with low or no flow due to system design and/or operation. The stagnant water in dead legs provides ideal conditions for biofouling deposits to form and Legionella to grow to high levels.</p> <p><!-- /wp:paragraph --><!-- wp:paragraph --></p> <p>A drain fitting was installed on the supply and return lines so that the dead legs could be flushed.&nbsp; A large amount of black, smelly sludge was removed from the lines which were flushed until clear.&nbsp; A cleaning and chlorine disinfection procedure was then performed with frequent flushing of the dead legs.&nbsp;</p> <p><!-- /wp:paragraph --><!-- wp:heading {"level":5} --></p> <h5 class="wp-block-heading">Results Achieved</h5> <p><!-- /wp:heading --><!-- wp:paragraph --></p> <p>The cooling&nbsp; system was returned to service and sampled for Legionella after one week of operation. The Legionella test result was negative. Recommendations were provided to install jumper piping across the dead legs to provide continuous flow.</p> <p><!-- /wp:paragraph --><!-- wp:paragraph --></p> <p><em>CS2-005</em></p> <p><!-- /wp:paragraph --><!-- wp:acf/two-cols-text-ctas {"name":"acf/two-cols-text-ctas","data":{"option_change_padding_block":"1","_option_change_padding_block":"field_6629e1de35327","padding_options":"py-to-60","_padding_options":"field_6629e0d2860af","background_colour":"white","_background_colour":"field_6629e20935328","block_options_clone":"","_block_options_clone":"field_662a2539a7d03","block_text_list_0_block_title":"","_block_text_list_0_block_title":"field_662a2573bc047_field_6629f36ac5d6b","block_text_list_0_block_excerpt":"","_block_text_list_0_block_excerpt":"field_662a2573bc047_field_6629f37dc5d6c","block_text_list_0_show_cta_button":"1","_block_text_list_0_show_cta_button":"field_662a2573bc047_field_662b4b6278ee7_field_6629f386c5d6d","block_text_list_0_block_cta_button":{"title":"Download PDF","url":"https://www.chemaqua.com/en-us/wp-content/uploads/sites/6/2024/07/CS2-005.pdf","target":""},"_block_text_list_0_block_cta_button":"field_662a2573bc047_field_662b4b6278ee7_field_6629f39cc5d6e","block_text_list_0_use_special_button":"0","_block_text_list_0_use_special_button":"field_662a2573bc047_field_663af6cb5a467","block_text_list":1,"_block_text_list":"field_662a2550bc046"},"mode":"edit"} /--></p>