The Shower drain is source of sewer odor but only after at least a day after it's last use. I popped open the drain cover & watched the water level in the trap & noticed the level moved up & down with the wind gusts outside. We've had fairly high winds over the past weeks. I did the other tests like flushing the toilet while watching the shower drain water level & there was no gurgling or change in trap water level. The wind gusts were the only thing that moved the trap water level up & down

Any solution? Perhaps the vent needs a wind protector?

Thank!

Good sleuthing on your part! Wind blows over the vent pipe, causes a negative pressure-venturi effect-and the water will actually lift. If a downdraft, you may find the same thing. However, I believe you will find the wax ring under the toilet needs replacing. First try to tighten the toilet down-CAREFULLY- and see if that helps. When the wind is blowing, see if the sewer smell comes out near the floor. If so, replace the wax ring. Vent caps are available and help in very windy areas, most mobile homes use them and they will fit over a regular house vent but I'd suspect the wax ring first.

Dummy me! It's the shower!! Forget the wax ring and go with the vent. Sorry, Brian

Brian, thanks for the confirmation. I'm here in Las Vegas & we can get some big winds especailly at night during major shifts in the weater. Will pick up a wind protector & find someone brave to climb the 2 story roof & install it! Do you know if the shower vent pipe size is standarized or do I have to go measure it?

Most vents are 1 1/2 and 2". The main stack is 3 or 4 ". I'd Google "vent pipe wind deflectors" or something like that for more info. There was a similar post like yours a couple of months ago so you may be able to find something there too. Brian