I live in a 50 year old house. The kitchen is on the main level on the west side of the house. The basement has a floor drain on the east side of the house. For about the last 3 months, whenever we run the water in the kitchen sink for a few minutes, sewer gas escapes from the basement floor drain on the opposite side of the house. We had a plumber come out to fix the problem. He verified exactly what we saw (and smelled). He rooted the main line from the floor drain and also checked that the vent stacks on the roof were clear. We're still having the problem. It doesn't happen when we take showers or use the washing machine on the east side of the house. It only seems to happen when we use the kitchen sink on the west side.

The plumber, a younger guy, said if the main line rooting didn't solve the problem, he would have his boss (more experienced) come out and do a smoke test. Isn't a smoke test to find hidden leaks of sewer gas? This isn't a hidden leak, as the smell is coming directly from the basement floor drain. I think a smoke test would be a waste of money, but I would like other opinions.

One other detail - we have a second kitchen sink in the basement, almost directly below the main-level kitchen sink. We never use the basement kitchen sink and about 10 years ago we capped it off - meaning we sealed the drain line from that sink with a cap. (I don't think this is relevant, but though I should mention it).

Thanks in advance to any expert advice!
Steve

Hi Steve

In one way, the plumber is correct in calling for a smoke test IF he cannot fix the issue by snaking the drain as smoke tests are used to find hidden leaks where sewer gasses can escape into the home.

However, I am a little confused with only the information provided. Does the waste water from the sink back up and out of the floor drain at any time? Have you run sink fulls of water or run a hose down the floor drain to see if you can get it to back up?

I would start here and see if I can get the drain line to physically back up and show that it is clogged.

Otherwise, I believe that the kitchen sink vent is clogged, non-existent or piped incorrectly as it sounds like the floor drain is only burping gasses into the home as a result of trying to vent the kitchen sink... make sense?

Check these things and post back, OK?

Mark

In the 20 years we've owned the house, I've never seen anything back up and out of the floor drain.

I haven't run a hose down the drain, but when we get the smell, we immediately pour several glasses of water into the drain and this seems to stop the smell from getting worse. Maybe it just stops on its own when we stop running the water in the kitchen sink however.

You might be on to something with the kitchen vent being clogged. The plumber went on the roof and looked down into the vent and didn't see a blockage. Is there a more reliable way to check for a clogged vent? If the blockage was low enough, perhaps his flashlight wouldn't have shown the blockage, right?

How do you clear a blockage in a vent? Shop-vac?

You can just run a hose up and on the roof and run water down the stack. Here, run water down the stack, but be sure to have someone inside keeping an eye on the sink in case water starts to back up and overflow the sink, OK? A kitchen sink vent would usually be 2" or it may tie into the main vent stack... if the K.S. vent ties into the main stack vent before going out the roof it will be hard to isolate and clear with the hose. In this case, I would advise cutting into the vent at the kitchen sink and snaking up the vent line... ;)

Also, if you do run the hose/water down the vent have that person checking the floor drain while you are doing this... see what happens while the water goes down the drain.

First, however, I would run a hose down the floor drain and see if you can get it to back up after a few minutes... if so, then the drain line probably needs to be snaked again.

Keep me posted.

I'll give it a try this weekend and report back. Thanks!