Holy Smokes

The only time smoking is good for your health

When you call the plumbers because your house smells like poop, they has several ways to try and find the problem. Looking at the vent lines extending above the roof can tell them if the vent is too close to a bathroom fan or the AC unit. When the wind comes up, sewer gas can travel along the roof line and enter the house through a bathroom vent. If it very cold outside, the air becomes dense, and the sewer gas doesn’t rise. It can fall along the roof line ands be picked up by the bathroom vents or the outside air supply for the heater/AC unit. If those things are not an issue, then there is a drain line that is not connected to the vent systema and is allowing smell into the house. This can be a floor drain that has gone dry, a toilet seal that has gotten old and dropped away from the bottom of the toilet or a clean out cover that is not fastened into place. We had a puzzler when we were trying to locate the source of a sewer smell in a state office building. They were getting a bad smell all the time

The building maintenance staff had put air admittance valves on all the building drain vents. An Air admittance valve will open to allow air to escape when water flows through the pipe but then closes to prevent odors from leaving the pipe. So, we tried what is called a smoke test. You plug all the drain vents to prevent the smoke from escaping, light the smoke emitter and look for the smoke. In this case, the smoke came out of the roof drains. This building was old enough to be covered under a previous version of plumbing code that allowed storm and sewer lines to be connected. When the smoke escaped the roof drains, it was picked up by the air handling units on the roof and discharged into the building. That was the cause for the sewer gas and how the smell kept coming back into the building. The solution would be to re-route the roof drains to a new and separate storm line system. Someone else got that job. Another time, there was a 5-year-old courthouse experiencing a smell from practically the first day of operation. They thought the smell was from the grease interceptor and had been hanging large bags of deodorant blocks under the lids, but the smell was still there. We blocked all but one of the vents on the roof and used 3 smoke emitters to fill the lines with smoke. The new courthouse was under construction at the time, and we filled it with smoke. We found the leak on the 3^rd floor behind a wall in an office. A 2” wye on the vent line to the roof did not have a cap on the open side of the wye. Once a cap was installed the air cleared and no more smell in the building. At another county building they had the sewer smell on the second floor in the office area. A smoke test revealed the drain piping for the AC units that had p-traps in them and that tied into the main sewer lines were dry and not forming a seal. We installed trap primers on these lines to keep the traps full of water. The smell went away. We had the Education building at the prison I work at get a bad sewer smell. The facility was only about a year old. Using smoke, we found a drain line for the de-humidified in a security electronics room dried out. This we treated with an oil-based trap solution to prevent the trap from evaporating dry. We did a smoke test at a restaurant to try and find a sewer smell. That test revealed several toilets which had the wax rings dried out and pulled away from the base. Replacing the wax rings stopped the smell. It may be dated, but it is still an effective way to find a leak.