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The Power of Peppermint

Fitzemeyer & Tocci Associates, Inc. (F&T) provided mechanical, electrical, plumbing, and fire protection engineering services at Worcester Polytechnic Institute (WPI) for multiple building renovation projects throughout their campus. Most recently, F&T completed renovations to Kaven Hall.

Kenneth C. Zirkel, CC BY-SA 4.0 <>, via Wikimedia Commons
Worcester Polytechnic Institute, Kaven Hall

Kaven Hall was originally constructed in 1954 on the corner of Salisbury and Boynton Streets and has helped to contribute to the Civil and Environmental Engineering Department. The current facilities include laboratories for civil and environmental engineering, structural engineering, geotechnical and water resources, environmental analysis, construction materials, and computer-aided materials and design.

The scope of the multi-phase project for F&T to a nearly 70-year-old building included lighting upgrades throughout the interior and exterior spaces and the modification to the existing electrical system to provide distribution to accommodate any new branch circuitry. Massachusetts Architectural Access Board (MAAB) upgrades were performed for access to the building and toilet room upgrades. Heating Ventilation and Air Conditioning (HVAC) upgrades included the installation of two new Air Handler Units (AHU) in the attic space. The fire protection scope included the reconfiguration of existing systems as well as providing coverage for floors currently without sprinklers and demolition and replacement of the dry attic system.

For the Plumbing scope, Phase 1 included supporting the contractor during the preliminary destructive investigation. Due to the age of the building, systems being buried in chases and trying to determine which systems were active and which systems were abandoned became a daunting task.

Phase 2 began the real design of the plumbing systems for the building. The plumbing scope included ADA upgrades to all the existing toilet rooms, enlargement of other toilet rooms to meet the minimum plumbing fixture requirement of the Massachusetts State Plumbing Code, and the installation of an oil interceptor in the concrete lab. The reason for the oil interceptor was due to the space having a roll-up door intended for access of vehicles into the space, another Massachusetts Plumbing Code requirement.

An issue came up during the end of the project when the building was getting ready to be turned over. There was a strong sewer smell in the building in the newly renovated bathrooms. Some suggestions included investigating the HVAC system to see if any air was being pulled from the exterior plumbing vents and into the intakes of the HVAC system. Since the plumbing vents were nowhere near the HVAC intakes, this suggestion did not identify the source of the smell. The next suggestion was to check all the floor drain traps to see if they dried out and allow sewer gas to enter the building. This suggestion provided some relief, but not completely. It was discovered that the valves feeding the floor drain trap primers were shut off, which allowed the traps to dry out. The valves were opened and the odors from the floor drains were taken care of, but there was still an odor on the second floor.

We scratched our heads to come up with an alternate possibility of finding the source of the smell. It would be difficult to find the source due to all the plumbing systems being enclosed in chases and behind finished drywall. I then thought of when I was a young engineer fresh out of college. My boss would always tell me when things were slow, to “read the plumbing code, you might learn something.” After some thinking, I remembered something I read almost 30 years ago during a slow time. In the Massachusetts State Plumbing Code, there are several ways to test plumbing systems that are commonly used, the water test being the most common. Other options are an air test, a peppermint test, and a smoke test. Since the water test and air test were not possible due to the systems being enclosed and a smoke test not being an option for the same reason, we recommended the peppermint test. I have never heard of this being used in my 30-plus years of engineering, but we agreed to give it a shot.

The process of a peppermint test is to combine a liquid mixture of hot water and oil of peppermint. The liquid then gets dumped down the plumbing stack. The top of the stack is then sealed. The person who makes the mixture and pours it down the stack is not allowed in the building until the test is complete to limit odor contamination. The idea of this test is that wherever the sewer smell is coming from will be able to be determined due to the strong peppermint smell in a specific location inside the building.

When the test was conducted, the strong scent of peppermint was immediate. It was in the second-floor bathroom in one of the stalls. Luckily, the bathroom had a suspended ceiling to make accessing the piping a little easier. Once the ceiling tiles were removed, it was easy to see where the smell was coming from. It was an old sanitary line that was left open. The Contractor had to get their skinniest employee to snake himself to the pipe. Once the pipe was sealed, the odor was gone.

Perhaps my first mentor after college was right; even when things are slow, you can make yourself productive. You never know when you may need the smallest bit of information to get you out of a bind.

Written by:

Richard Barbera

Plumbing Engineering Manager at

Fitzemeyer & Tocci Associates, Inc.


Kenneth C. Zirkel, CC BY-SA 4.0 <>, via Wikimedia Commons


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