With a tap that far away, your trap and trap arm must be 3 inch, and your slope 1/4 inch per foot (no steeper). I suspect your line size is too small which can cause the trap to have too-low water level, allowing gases to get through.

I have never heard of the trap being located that far away. Head on over to the Terry Love Plumbing Forum, giving your location, to get specific recommendations for repair.

Thank you all for responding!! The p-trap is embedded in concrete and was not replaced as far as I know, but all other pipes / plumbing were replaced. I dug up a pic from during construction and the second pic shows the copper drain pipe is pitched, please let me know what you think.

With the tub on a platform, why in the world would the ptrap be placed so far away? Your drain line is not 3" - therefore your drain diameter/length ratio is inadequate. Any licensed plumber should damned well know better.

Hi Alice, Thanks for your feedback, sounds like our only option at this point is to pull the tub out and put a second p-trap in the tub's platform.

Two p-traps is generally contrary to code as well. Your plumber(s) just need to do the job right.

unfortunately, pulling out the drain pipe and installing a new larger one isn't possible, too many things in the way, we would have to tear apart half the bathroom.

Would having two p-traps cause any problems in the future?

We can't remove the existing p-trap, it is embedded in the concrete floor, so all we can do is add another one under the tub.

A second trap under the tub might resolve the odor problem, but it may cause new problems and prevent the drain from flowing properly, which is why it is generally prohibited by code. Having two traps can cause a vacuum to occur and the suction can empty out the P-trap, or cause sluggish, irregular flow. Another reason two traps in series is frowned on is because it makes it difficult or impossible to snake the line if you need to.

Have you tiled the floor yet, or is the concrete still visible? If the concrete is accessible, it would be advisable to jackhammer the area where the existing P-trap is located and replace it with a straight pipe section so you can do a new P-trap properly. Jackhammering is not that big a deal for such a small area, even though it sounds drastic, and it would be easy to patch if you are then covering it with something else like tile.

If it is totally impossible to remove the existing trap, the only other suggestion I can make is to see if it is possible to add a vent near the new P-trap under the tub and vent it up the nearest wall. Normally venting goes through the roof, but you might be able to simply run the vent pipe up inside the wall cavity to about the 4' level and cap it with an air admittance valve. AAV's are allowed in many localities in installations like this as long as there is a cover plate on the wall that you can remove to allow inspection or replacement of the device.

The other question I have is where is the vent for the tub now? If it is in place near where the new P-trap would be, then that helps a lot. If it's far away at the existing P-trap, that may be another code violation, unfortunately.

Hi Kudzu,

Thanks for responding!

The remodel was completed over a year ago. Unfortunately the sewer smell was not detected until after we moved in. I believe the existing trap is part of the condo building and we may not be allowed to remove it as part of it extends a couple inches into the condo below us.

Will the AAV allow sewer gases into the condo?

In the second pic above, there is a large copper pipe a few feet above the drain pipe, is that the vent you are asking about? It looks like it extends from near the tub back to the existing p-trap.

Thanks again,

s

I've looked at your pictures and could not figure out what piping was for what. Copper is not usually used for venting because it is unnecessary and expensive in that applicaton; I'm not saying it's impossible, just unlikely. Black plastic ABS is the typical vent you find these days.

An AAV is a device that has a flexible seal and is normally closed to prevent entry of sewer gases into the living space. When you drain a tub or flush a toilet, the flexible seal opens up to let air in and prevent a vacuum from occurring in the drain piping (a vacuum would interfere with the proper action of the drain). As soon as the water is finished going down the drain, the seal closes back up.

How an AAV works