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Richardson Engineers to Use Smoke to Test Sewer System

Post Date:07/12/2019
The City of Richardson has contracted with RJN Group to identify sewer system infiltration and inflow by using a smoke leak detection process. The smoke is nontoxic, harmless and has little odor, but it could be very visible in areas where leaks are detected.

About the Testing
Smoke testing is one technique used to identify areas where unnecessary groundwater or rainfall is entering the sewer system. Using nontoxic smoke candles, smoke is forced through the sewer pipes using blowers placed on top of manholes. Anywhere the smoke exits, there is potential for rain or groundwater to seep into the sewer system.

Smoke-Test-Complete-MapTesting Area

RJN is scheduled to begin smoke testing on the Cottonwood Creek Drainage Basin beginning in July. The basin (see map to right) includes about 97 miles of sewer lines. The city has about 410 miles of underground sewer lines in place. 

The duration of the project is expected to last through October, weather permitting, but testing on specific streets within the study area should only take approximately 20-30 minutes.

Community Notification
At least 24 hours before smoke testing is scheduled to start, RJN will place door hangers on the front door of every building where testing will be conducted. RJN will also visit businesses in person to notify operators of the testing. Roadside signs will be prominently displayed on the street when smoke testing is in progress.

At no time will field crews have to enter a residence but you may see them walking around your property to record leaks. RJN staff will be dressed in RJN-logoed uniforms and will carry identification badges. Crew members operate from vehicles with RJN signage.

The City of Richardson will send out direct notifications using Nextdoor social media prior to the testing beginning in a neighborhood. Residents can sign up for an account at

Where Smoke Will Occur
Smoke will be visible from any area where a leak is occurring. During this testing, smoke may be noticed exiting through the ground, vents or pipes on the roofs of homes and through sewer line breaks. The smoke is nontoxic, leaves no residue, and creates no fire hazard.

The smoke should not enter a home or business unless defective plumbing exists or drain traps are dry. If it does, residents are asked to pour a small amount of water in seldom-used drains to fill the trap and contact RJN staff working in the area.

Residents Asked to Fill Drain Traps
Drain traps should always be filled with water to prevent sewer gases from entering the building. About three cups of water should be poured in floor and sink drains, filling the traps to prevent smoke from entering the home. If smoke does enter, it could set off smoke alarms. The resident should also consult a licensed plumber to ensure there is no faulty plumbing, which could create the potential for dangerous sewer gases to enter the home. People are asked to contact a member of the smoke testing crew working in the area if smoke is noticed entering a building or structure.

Why Testing is Being Done
Smoke testing is a cost-efficient technique used to identify areas where unnecessary groundwater or rainfall is entering the sewer system. Stresses on the sewer system from such leaks can cause backups, overflows, and higher costs for sewage treatment.

More About Smoke Testing
Smoke testing has been used for more than 50 years to detect inflow and infiltration of external water sources in sewer systems. Smoke tests were conducted last summer in the Floyd Branch Drainage Basin. City of Richardson engineers plan to use smoke to test the entire sewer syste
m in segments. The work is expected to be complete in the next five years.

Contact Information
Anyone with questions regarding smoke testing can call Tristan Nickel at 972-437-4300 or e-mail Padma Patla at
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