smell in downstairs bathroom

We have a weekend house that has two bathrooms, kitchen sink, dishwasher and a washing machine. When we first arrive at the house on Friday nights, we turn on the water and the water heater. After the upstairs toilet is flushed, a terrible odor starts in the downstairs bathroom. It seems to be worse by the sink, but not sure - the whole room starts to smell. We have periodically used baking soda, which works for a little while. And Ridex once a month for the last three months, but nothing has helped. It is particularly bad on windy days. We have also had problems with ice forming at the top of the vent pipe, but that only lasted a few days. The bathroom sink has a trap that is like a full loop, not just a p-trap. Not sure if that matters. There is a shower, toiler and sink in the bathroom. Each waste pipe from the fixtures doesn't appear to be individually vented, but I guess the main waste is vented?

Help - we are having company soon!

Sounds like a smoke test is in order to determine where the sewer gases are emitting from. A plumbing supply house will have 3 and 5 minute smoke bombs, use a shop vac for blowing air towards the house from a cleanout outside. Any visible smoke or smell of smoke in the house will lead you to the problem. Most likely could be a leaking wax ring. If you ever pull a toilet and the wax ring is blackened, that is where sewer gases have been travelling between the toilet and ring, not a good air-tight seal.

smell

Is there be a floor drain that needs to be checked?

stinkhouse said:

bathroom sink has a trap that is like a full loop, not just a p-trap.

Click to expand...

Is this an S-trap? Water being sucked out of the trap?

Jason

thanks for the help

Thank you to everyone who responded.

We don't have an exterior cleanout that I know of - just the cleanout prior to where the pipe exits the house and then it goes to the septic system. Is there another way to do the smoke test?

There aren't any floor drains in the house, except for the showers.

I guess that weird trap is called an S trap. Are they known to have water get sucked out of them and break the trap? When we do smell it, we try to fill the shower drain and the sink, but the smell still continues. Could that still maybe be from the S trap?

yes... an s-trap will siphon more water out and break the water seal that a p-trap provides. I would definitely change that to a p-trap!

I had a problem with a smell coming out of the bathroom sink and found it was coming from the overflow. The sink is one of those plastic molded one-piece faux marble units. The trap seal is working.

I solved the problem by squirting a little straight bleach into the overflow to kill whatever was growing the smell. The cabinet under the sink now has a mustard squeeze bottle (make sure you use one marked HDPE) filled with bleach. When the smell recurs, it gets a couple of squirts and the problem is solved for a month.

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