Been a while since I posted but need some help/guidance. Having a smell in kitchen area from under sink. I've replaced the vent cap two times. I've taken the trap off, cleaned (pretty empty) and replaced. I've run really hot/boiling water down the sink (several times), but still am getting a smell. I just sealed the holes thru the floor with the expandable foam. it doesn't appear to be a leak (no water anywhere). I also shut the grey tank off and filled/treated and let sit overnight and then flushed it out. I've checked under trailer for leaks and have found none.....didn't take the under cover off but did not see any drips, etc. I am at a loss on this one. just not sure what to do next???? BTW, no smell under the sink in the bath room area at all from the second grey tank (shower and bath sink) and it also has a vent cap on it. While I am staying in TT for winter I leave black closed til dump time. I leave grey tanks open til day before black tank dump schedule and then close them for extra flushing of line after black tank dump but then leave them open again til next time. Crack in grey tank?, Crack in line somewhere? I'm lossed .... Am I missing something here?