Originally Posted by Bchtravlr
On our 2020 MA we have struggled with sewer odor .....
Tom, there is no reason to be using any kind of deodorizing treatments in your newmar tanks. They are sealed. When there is tank odor present inside the coach, one of the vents is bad or the anti-siphon valve is gone bad. Assume you have the dometic toilets with the macerator (very likely)?
behind the toilet look for the siphon valve behind the toilet, see pic. if you see yellow/brown discoloring (in the white area), it is likely that the valve is leaking.