Sewer smell coming from under sink.

[Mike.Merrill.76]

Keystone passport 2013 2910bh. Experiencing an unusual sewer smell from under the kitchen sink. Could the black tank be backing up into the grey water lines? I don't think they are connected. Haven't took the traps off to see what's going on because we are camping for spring break. Don't feel like working on vacation. Any input would be helpful. Thanks.

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[Festus2]

Sometimes, this odor is caused by a malfunctioning "cheater vent" which takes the place of the usual galley holding tank vent. Look under your sink and you may see a black PVC pipe with a spring-loaded cap on it. The cap may have worked its way loose or the mechanism inside has failed.
These cheater vents are often easily purchased at HD or some other big box store and are simple to replace.

[cw3jason]

Same as above, but I'll add if you are hooked up to the sewer, keep your dump valves closed until your ready to dump. This will prevent any of those gasses from coming back up into your trailer.

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[theeyres]

It had happened to me and it is that vent under the sink, used instead of an air pipe going up to the roof. It's a five minute job and $20 part. It's called an Air Admittance Valve.

[JRTJH]

The easy way to determine if it's the "cheater vent" that's actually allowing the smells to enter is to take a plastic sip lock bag, slip it over the vent and tape it to the pipe. If the smell persists, it's not the cheater vent, but if the smell goes away, replacing the vent will fix your problem.

[Elk4me]

The easy way to determine if it's the "cheater vent" that's actually allowing the smells to enter is to take a plastic sip lock bag, slip it over the vent and tape it to the pipe. If the smell persists, it's not the cheater vent, but if the smell goes away, replacing the vent will fix your problem.

Don't forget to remove the bag and replace the Air Admittance Valve. If you don't the next time you dump the gray water tank you stand the chance of the outgoing water flow will produce a suction on the drainage system which will suck the water out of the P-Trap under the sink and the sewer gas smell will really be strong. The water in the P-Trap keeps the smell out by providing a water seal.

[JRTJH]

Don't forget to remove the bag and replace the Air Admittance Valve. If you don't the next time you dump the gray water tank you stand the chance of the outgoing water flow will produce a suction on the drainage system which will suck the water out of the P-Trap under the sink and the sewer gas smell will really be strong. The water in the P-Trap keeps the smell out by providing a water seal.

Yup, YUP !!! Any time you use a "Band-Aid fix" to check something, ya gotta remember to "undo the Band-Aid" after you verify the condition !!!

That said, I wonder if the OP ever resolved his problem???