I recently sold my home and had to install a radon mitigation system (RMS) prior
to the sale. Now the buyer is having major sewage issues with backups, raw sewage, smell and sewer gnats and the basement toilet is unusable. The sewer gnats are inside the home and also flying outside through the RMS vent. There were no plumbing/sewage issues or sewer gnats whatsoever while we lived there. The only change is the RMS which is installed only 2-3 feet from the basement floor drain. Have you ever heard of any problems like this? How can this be resolved?

If the floor drain is connected to the sewer system, then the trap is dry and providing a path for the flies to enter the house. It does not explain the other issues you describe.

if installed properly, one has nothing to do with the other.
when you were mandated to install the RMS did you take the lowest bid?

If it was installed correctly, then it is a passive system without connections to ANYTHING.

Have the new owners clean the drains and get them video inspected at their own expense. If there is a problem, they can deal with the company that installed the radon system. The only situation that would explain it other than typical drain problems, is if the radon folks broke the concrete, and drove something through the sewer line and caused damage. It is highly unlikely that this is the case, and more than likely somebody flushed something that they shouldn't have.

Wonder if the radon system was incorrectly tied to the basement drain, so it's sucking the trap dry?
Was it a reputable firm, or just a guy?



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with the main line backups, the water draining out of the system is probably siphoning the floor drain traps.

My realtor recommended this contractor. There were no bids as we were 2 weeks from closing.

I believe a camera was put down there by an inspector during the sales process with no problems found. The buyer said they put 4 bottles of Drano down the sink the first time they had a problem. Since then they had a plumber flush it out and put a camera down the sewer line. They said there are some small cracks - the house is 50+ years old. I suggested they turn off the radon system to see if that helps, but they refused.

My plumber said that there are rocks under the basement floor and that they are probably being stirred up by the vacuum created by the radon system.

Long story short, if the sewer was video inspected prior to the new owner taking possession and it was found structurally intact, then the sewer backups are not your problem or concern, and were caused after the home changed possession.

Radon is a colorless, odorless gas that can leak through cracks in building foundations. The U.S. Environmental Protection Agency calls radon the second-leading cause of lung cancer in the U.S. The agency also says Iowa's 99 counties are in the agency's highest risk zone for exposure.