Troubleshooting Sewer Odor in Bathroom

Troubleshooting Sewer Odor in Bathroom Troubleshooting Sewer Odor in BathroomA sewer odor in the bathroom is a common household problem. It is usually something simple that is going wrong with the homes drainage waste and vent system. To troubleshoot a sewer smell in the bathroom, we just need to go through a list of common problems that cause sewer odor until we find the cause of the smell.Troubleshooting Sewer Odor in Bathroom.

1) The sewer odor is coming from a drain trap.

Check all the drain traps and p-traps. If you have a plumbing fixture such as a floor drain, sink, bathtub, etc. that you dont use often, then the trap could easily dry out over time, and if there is no water in the trap, then the septic odor can waft right out into your home.

Traps are the part of the plumbing drain that is U shaped and keeps the sewer gases trapped in the drain system. If you have an old floor drain, often that is the problem as they rarely get used, and quickly become dired out.
2) Check that your drains are properly trapped and VENTED.

Studor Vent Troubleshooting Sewer Odor in Bathroom
The plumbing vents allow the gas to escape, and also allow pressure differences to balance out so when you use a drain, the trap is not siphoned out. Without drain vents, the traps would not function right. Nowadays, a lot of people try to fix their own plumbing, or do their own remodels and many of them dont really understand how plumbing works.

I have seen many homes where the traps were installed wrong, or installed without vents, or vented improperly. If you have an s-trap then that is against code and could be causing the odor issue. S-trap arent vented and can easily be siphoned out when the drain water goes down, thus breaking the trap seal and letting sewer gas and odor through.
3) Check for a bad mechanical vent, or air admittance valve.

Another common modern feature is the air admittance valve, or studor vent or auto vent or mechanical vent. Auto vents can be used in place of regular plumbing vents in certain jurisdictions and applications. They work by letting air IN to the system to prevent trap siphon-age, but they dont let air OUT. Thus the name air admittance valves. If you have an auto vent, it will usually be located underneath a sink, or in a small panel in the wall above a plumbing fixture.

They are as easy to replace as changing a light bulb, you just need some pliers and some Teflon tape.
4) Check your toilet seal for an odor.

A VERY common place for sewer odor to get into the home is the toilet seal. The wax seal at the bottom of the toilet seals the toilet drain system. Since toilets have integral traps, the toilet bowl itself traps the water and seals out sewer gas. However, underneath the toilet where the wax ring seals it to the flange, gas can escape if this seal is not set properly.

Check by flushing the toilet and sniffing around at the bottom area. The flush may allow some gas to come through.
5) Do a smoke test or peppermint test to locate the source of the odor.

If after following the above steps, you still can;t find where the sewer smell is coming from, you could hire a plumber to do a smoke test on the drain system, or a peppermint oil test. They will seal off the system and drop peppermint oil down the main vent stack on your roof, or blow smoke into the vent. The idea is that the drain and vent plumbing system should be sealed, and any leaks will allow the smoke or the peppermint smell to come out wherever the leak is and make its location very obvious.

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One Comment

  1. Kathy
    Posted February 22, 2011 at 9:26 pm | Permalink

    The odor I get is only when we take a bath and drain the tub. Originally thought the odor was coming from the tub drain but that is not the case. When the water drains the odor (that smells like rotten eggs) is coming from the toilet. This did not start until we had the bathroom remodeled and put down a tile floor and had a new toilet installed. The first time t his happened the plumber came back and said the wax ring wasn’t sealed. That helped for a while but now it’s happening again. Someone told us to caulk around the bottom of the toilet and that should eliminate odor. Again, this doesn’t happen when we take showers and the water is draining, only when the tub drains. Any suggestions?

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