I have a 2010 Bighorn 3055RL. Occasionally I get a sewer gas smell under the kitcher sink. I examined pipe and fittings for any apparent leaks. Looked OK. When I unscrewed a spring loaded vent on top of the vent pipe under the sink I found the disk in the valve glued down with a lorge puddle of solvent glue. I assume that this is not a factory modification? Will this valve, not functioning, suck gas back into the camper? Any other suggestions. I did check the top cap on the vent line and it looked OK.