I have a basement floor shower drain which occasionally omits a sewer gas smell. I pour water down the drain to stop the smell, but its back in a few days. This is a standard 3" floor drain in concrete. I was wondering if there is a drain made that will surface mount in the floor with some type of flapper or check valve built into it to prevent the gas backup?

Hi Btempl

They do in fact make such a device, called a sure seal, for shower drains and floor drains... see images below.

You can also click on this link for more info.:

SureSeal | Inline Floor Drain Trap Sealer

Another option is the trap guard. Click on this link for more info.:

http://www.trapguard.com/

With all that being said, I have to wonder why the drain is "burping" the sewer gasses? Have you tried snaking the drain or the vent associated with the drain?

Let me know...

Mark