I have a problem with sewer flies.
We have sewer flies in our utility room. We have had a plumber check the sewer line with a camera and smoke tests done too. There is no evidence of any cracks. What should we do next? How do we check under the slab?
Sounds like you may be dealing with drain flies. See our website for photos and control information. You need to find a breeding site or sites. Sounds like you have no leaks. If you find the issue are drains, clean the traps and drains mechanically or an over the counter drain cleaner with enzymes followed by hot water. You can find these enzyme drain cleaners in big box or home improvement stores. http://extension.umd.edu/hgic/drain-flies