Mold problem from sink, can't figure out

[Bob B]

Hello all, first time posting, so here is my dilemma, for several months now we have had a mild to severe mold smell in our kitchen. We figured it out finally that is coming from our double sink drains. Backstory to this goes as this. Last fall we had a strainer issue pipe corrode issue, we hired a plumber to come in, he replaced strainer and pipe to plastic version, while doing that he added new p trap and a back flow preventer, not sure about this we have never had a problem, so fast forward a month or so later, this back flow preventer makes awful whine noise when you dump or drain water, and now out kitchen smells like mold, I have tried every DIY home trick, we have no garbage disposal, we have double sink, dishwasher hose attached to right side of drain. We never had a problem in the past until the plumber did this work. Not saying he caused it and it may have been just something else pop up. I have had no further professional plumbing action since, have used drain cleaner, bio material, peroxide, hot water, bleach, soap, fan into drains, we are lost and besides professional plumber again looking for advice. I am enclosing pics of the underneath of our kitchen sink.

 

[frodo]

the problem is that hose, it needs to be looped up to the bottom of the cabinet, tie off, then down to tie into the y branch tail piece.

question, why do you have an auto vent fitting under the sink? it needs to raise up as high as possible also
and, the auto vent,,,could be stuck open causing the stink also.

look on your roof above the sink, is there a vent pipe?

 

[TomFOhio]

Also that AAV is incorrect. You should have an Oatey or Studor Air Admittance Valve. The black AAV that you have is
used for mobile homes around here. You can change that yourself. Also take care of the dishwasher drain hose like
mentioned and then see if your smell goes away.