Sewer odor in newly modeled bathroom


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Old 07-11-08, 02:22 PM
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Sewer odor in newly modeled bathroom

We have a sewer odor our newly modeled bathroom on the first floor. The toilet used to have a lead bend attached to a brass flange. The lead bend connected to cast Iron to the basement main line. the main vent line went up the bathroom directly above and is used by the shower, toilet and sink on the second floor.

The plumber said our 75 year old cast iron/galvanized waste stack line in the crawlspace under the 1st floor bathroom was rotted so we replaced the entire waste/vent stack line from the basement to 2 ft beneath the second floor, replaced the entire toilet lead bend/cast iron with PVC and a brand new PVC flange. I watched the plumber to make sure the bottom of the flange was flush with the tile. and we replace the sink connections with PVC. Basically it is fully brand new PVC from right below second floor to the basement.

The problem is that the bathroom still smells even though we replaced the waste line. Also, the 1st floor toilet and sink are BRAND NEW.

I did notice that water is beading on the bottom of one of the connections in the crawlspace under the bathroom. Could this be the source of the persistent odor since if i see water (small amount), the gas must be leaking also?

I used a flastlight to look at the sink P-trap and it is full. I confirmed the toilet has water and the tank has water.

What else can I do to eliminate the odor? Where is the odor coming from.

Is it possible the leak is in the vent pipe on the second floor and the methane gas which is heavier than air is sinking which is why the first floor bathroom smells?

All the toilets flush fine and shower drains so i doubt it is clogged vent issue.

Thanks for the help in advance!
 
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Old 07-11-08, 05:28 PM
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For you to have sewer gas in the house, irregardless of a disconnect, a clogge vent, no water in a trap (including floor drains and washing machine stand pipes) - you must also have a condition where the house is under less pressure than outside the house. Did you smell around the base of the toilet(s)?, as you can have a toilet that does not leak on the floor when flushed, yet sewer gas can really pour out between where the bowl meets the floor, if the house is under negative pressure. Not some theory: Been there/solved it.

Hopefully someone did not forget to glue one of the joints. (But for it to send gas into the room, as stated, you also have to be under negative pressure.)

Things that can cause negative pressure besides an atmospheric inversion are a chimney in the house (including a vent for a gas water heater), or a window open only on the downward side of where the wind is blowing from (a venturi effect), or from exhaust fans or dryer running in the house.
 
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Old 07-12-08, 07:11 PM
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Sewer odor in newly modeled bathroom Reply to Thread

You gave some interesting theories and ideas. However, can you explain what i can do to help resolve the problem in the context of these ideas.

We did have a plumbing code violation we resolved were the small flue (hot water heater) in basement was below the big flue (furnace) or other way around. in any case, a plumber tied them together into the big flue. He then filled the small flue hole with plumbers putty. I am not sure if that is related but i assume that the flue is not blocked.

I will be calling our 4th plumber to look into the problem. Are there any special tests he (or I) can run that can locate the source of the problem?

I would expect that even under negative pressure, if there were no leaks in the pipe joints, it should not smell since all smells would be vented up the stack.

Thanks
 
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Old 07-12-08, 08:00 PM
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Hello, and welcome to DIY

I don't care about positive or negative pressure in the house, you should never smell sewer gases in the home if everything is installed properly. That is the purpose of the water seal in the traps and the wax seal.
If you are on a city sewer, it is possible to have positive or negative pressures in the sewer pipe, which can indirectly cause the trap to siphon, creating sewer gases. Improper venting can also cause the same effect.

I would be looking for a bad wax seal, or a pipe that has not been connected or capped off properly. Does the drain go into the wall under the sink or into the floor? If it goes through the floor, you may not have a vent and it is getting siphoned enough to cause a smell.
 
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Old 07-12-08, 09:56 PM
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Sewer odor in newly modeled bathroom

Excuse the crude drawing but it is a rough image of the plumbing in the house.

All the plumbing in the red box is brand new PVC.



Also, it is ONLY the bathroom on the first floor that smells. There is no odor in the bathroom above.

Any additional thoughts?
Thanks!
 

Last edited by zbeck; 07-12-08 at 09:57 PM. Reason: update
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Old 07-12-08, 10:35 PM
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hi,

If the first floor is plumbed the way the picture shows, you have no vent for the 1st floor bathroom. Every time the 2nd floor bath is used, it could push or pull water from the 1st floor trap. I will work up a drawing to explain, but it will be later.
 
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Old 07-12-08, 11:09 PM
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Sewer odor in newly modeled bathroom

Please do when you have time. I can envision exactly what you will draw as I am reading your posting. I would guess a second stack that connects to the main stack ABOVE the wet portion of the line which is some point above the sink on the second floor.
 
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Old 07-13-08, 09:46 AM
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This is a typical wet vent group. Omit the 2" line going to FD and this is how your bathroom should have been piped.
Notice hao everything from the 1st floor bathroom is all connected on one branch and seperately back vented.

The 3" soil stack is serving the drains from plumbing fixtures above.
The 1 1/2" back vent on the lav will continue up 6" above the highest fixture flood level and then may tie into the vent system.


http://gs249.photobucket.com/groups/...ng_wetvent.jpg
 
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Old 07-13-08, 06:35 PM
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Sewer odor in newly modeled bathroom

ok. Just to make sure I got this, i updated my little diagram the way it should be properly plumbed. please review and make sure i got it right.

Also, after running the tub upstairs and the toilet upstairs, i check the downstairs sink trap and it was still full. Also, the toilet was full of water. I assume as of now, the traps are not the problem but the leaky pipes since it still smells.

Thanks!

 
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Old 07-14-08, 06:42 AM
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Yes, that drawing shows basically how it should be piped.

In lieu of the back vent, an "air intermittance valve", when allowed by your inspector, and if you have construction issues preventing conventional venting. This would be installed under the lav on the branch coming out of the wall. But don't forget, it is a mechanical device that will fail at some time.

I guess I would fix the leak(s) and then see if you still have a smell.
 
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Old 07-14-08, 07:32 AM
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Originally Posted by plumbingods View Post
Hello, and welcome to DIY

I don't care about positive or negative pressure in the house, you should never smell sewer gases in the home if everything is installed properly. That is the purpose of the water seal in the traps and the wax seal.
I could say I don't care about a lot of stuff, also. But that is WHY you smell the gas. I have had many experiences of even loose toilets, SEVERELY loose toilets - with no sewer gas! Same with open floor drains. If there is the proper updraft up the vent stack, you won't smell sewer gas even if parts are loose and no water in the trap, if the inside of the house is more positive pressure than the outside. The only REASON for being able to have the gas not go up a clear vent stack is if the house draws it back in.

The poster have had his mind made up, that since there are no water leaks and traps have water, that he has not addressed the issue of the possiblity that sewer gas CAN (and will, most likely) come out at a (ill-fitting) toilet wax seal, even if there is no leak on the floor, and all the water is in the bowl. All because of negative pressure.

It's just a scientific fact that SOME people might like to know about as to WHY something occurs, more than just the fact it occurs.
 
 

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