Nova novent and sewer gas smell

I live in a small, older house. The plumbing is all new PVC, but installed before I bought the home. There is one make “stack†that the toilet, sink, and shower all drain into. This is vented well through the roof. The kitchen sink is across the house and does not have an exterior vent. It has a Nova novent. What can you tell me about these? I have been noticing sewer smell in the house. Is the rubber prone to failing? Is the entire device prone to failing? Obviously the best thing I could do is place a vent stack to the roof, but are these devices an acceptable alternative.

Thanks.

I'm not familiar with the term, but it sounds like it is an air admittance valve. These are also called Studor vents. It may be that it has failed as you have guessed. Before I would punch a hole in the roof for a new exterior vent, I'd replace the old until. They're very inexpensive and those I have used all screw into a female adaptor on top of the vent pipe. There are supposed to be installed in an easily accessable place.

vent

They are an "approved" substitute in many areas, but whether they are an "acceptable" substitute depends on the plumber you ask about them. They will create problems that don't happen with a conventional vent, such as preventing drainage, and also leaking when the valve sticks or wears out.

is it common for them to fail?

If the odor is near the sink try replacing it and see if the odor goes away. Check the basket strainer for a leak that keeps it wet but doesn't drip this can cause a similar odor.