Sewage smell thru bathroom sinks

[heater963]

Hello,

I am new to this forum and have a real problem. I purchased a home and we recently noticed that in two bathrooms at separate ends of the house that sewer gas seems to be coming in thru the sinks. The sinks all have P traps and drain normally when filled. I went under the house and had my wife flush the toilet, while I held my hand around the sink drain pipe. It felt like the 3" toilet pipe to the 3" main drain was forming a suction or vacum as the water from the toilet rushed down the main drain. I think the suction is removing the water from the sink P trap, enabling septic tank gas to flow up thru the sink drains.

Both sinks have a 1/12" drain that are glued to multiple ABS pieces that connect under the house to a 2" drain, which connects to the 3" main drain. I checked the vents ion the roof and they appear to be open and have sewer gas coming out of them as well. Is it feasible to install an Air Admittance Valve under each sink and thereby alleviate this problem?

I have no idea if the involved sinks are connected to the vent stack system and did not want to tear my walls apart to determine that answer. Can an AAV be installed when an existing vent stack is in place? I live in California, which may or may not have some codes that "normal" States do not concern themselves with.

Any help here is deeply appreciated. I know this is dangerous and I am concerned for the health of my family.

 

[phishfood]

I am wondering just what you mean when you say that

I went under the house and had my wife flush the toilet, while I held my hand around the sink drain pipe.

If you are under the house, there should be no open section of the piping for you to hold your hand around, the drainage system should be a sealed and continuous piping system under there.

Sewer gas is nothing you want in your house, your concern is well placed.

 

[heater963]

Hi,

I simply meant I placed my hand around the exterior of the sink drain pipe and could feel what felt like water being sucked out of the sink drain pipe. My theory is the toilet being on a 3" pipe and draining into a 3" main drain to the septic tank is creating a vacum of sorts in the 2" sink drain pipe as it goes by the 2" pipe, which is also tapped into the 3" main drain. I believe this suction may be strong enough to remove water from the P trap in the sink drain, thereby allowing sewer gas to flow up the pipes and out of the sink drain into the house.

We also hear a whistling sound shortly after the fixtures are used. It is not a water hammer per say, but a whistling sound that comes and goes about 3 to 4 times and subsides.

Whoever built this house did not know what they were doing. The other day my friend brushed a bullnose on the counter and it fell and broke. They mortared expensive bullnose tile to a wood substrate, which expands and contracts. Today, I removed almost half of them as they were about to fall as well.

I bought a Money Pit that looks beautiful!

Have you ever heard of what I am talking about? This is my number one priority because I realize it can make everybody sick.

 

[Zanne]

Heater, I'm no expert, but it sounds to me as if your sinks may not be properly vented. So either they do not tie in to the vents at all or are not tied in properly.

IIRC, according to the code, the vent pipe must remain vertical for at least 6 inches above the flood level of the highest fixture it services.

Now, I could be wrong, so its best to see what more of the experts here say, but my guess is improper or nonexistent venting.

 

[heater963]

I have the same belief. I don't know how to determine if the sinks are vented, without tearing the walls apart to visually see the vent stack. It definitely seems like a pressure differential problem, which is what the vent does as I understand it. I am not a plumber, but I know gas would not be coming from the sink drains if the water trap maintained water in it. Thanks for your help here. I know the answer is out there and I simply can't afford to hire a plumber, nor do I know one locally that I can trust. I just moved here in March and I have been fixing problems ever since the day I moved in. The "plumber" used a claw hammer to run various lines into the attic from the basement. The house was vacant for 5 years but "new." The second night I heard noises in the attic. I had the forest in my attic, having babies, nursing etc. It took a full month to screen off all the openings. It has been a real field trip! Thanks again!

 

[phishfood]

Look at the roof in the area of the bathroom sinks, and see if there is a vent pipe through the roof there. There also might be an air admittance valve underneath the sink, it would look something like this link:http://www.google.com/imgres?imgurl...woQUvq3EcXuyQHvioCoBg&ved=0CFEQ9QEwCg&dur=352

From your description, it does sound like a venting issue.

 

[Zanne]

I wonder if an admittance valve would work with my sink setup... Thanks, phishfood.

Heater, I know what you mean about having a hard time finding someone reliable. Angieslist costs money but sometimes there are ratings on people on yahoo-- not always though. I haven't really been able to find a good plumber since my old one passed away.

One thing you can do is ask someone from the local Department of Health if they could send you a list of plumbers in your area who are licensed. They keep lists by county and you can ask for any in your county as well as other nearby counties. From there you can look them up on google or yahoo or yellowpages (or all three). If you can find an e-mail contact for someone in the department it would be a good start. Barring that, you could call and set up an appointment to meet with someone in the office and get the data-- or ask for an official url that would lead to a list of licensed plumbers.

I hope you get this sorted out soon.

 

[heater963]

Hello phishfood,

I do not have any AAV's. I did look at the vent stack on one of the two affected bathrooms over the weekend. The sink, toilet and tub are vented, which is a relief. I went into the attic and found that the "plumber" had taken the stack vertical into the attic and placed a 90 degree elbow on it once he got into the attic. He ran a horizontal line approx. 14 feet with no slope to it. He placed another 90 elbow and went vertical to the stack that goes thru the roof. The exterior portion of the stack was quite low and the pitch of the roof is at least 3 feet above it. I placed a 2 foot additional riser on the exterior stack, in the hopes it helps. i read that living in a canyon can sometimes cause downdrafts into the venting system, which is amplified if the soil stack is too close to the roof. This home is located at the bottom of a 1,000 foot canyon, so I began with the simplest things first. A $2.00 stack extension.

I have a funny feeling the smell will be worse come cold weather time, as the gas will condense and sit in the 14 foot horizontal line of pipe, that has no slope to it. Why they did not just keep it vertical is beyond me.

I know you are a plumber and I suspect you will confirm the 14 foot horizontal run is a problem and a great place to start in terms of placing a slope on that vent. What do you think? Am I on the right track here?

Thanks very much.

Heater

 

[Zanne]

Hmm.. I'm wondering about the horizontal line as well. I could be wrong, but once it goes beyond the initial 6 inches above the flood level, I don't know if the angle really matters too much since it isn't like water-- but then, air is affected by gravity as well, so it might just be sitting in there.. I really don't know. I'm hoping someone will answer this.

I looked it up and from what I've read, the vent needs to slope 1/4-inch per foot upward away from the fixture.

Still hoping someone who actually knows about this stuff can answer though.

 

[heater963]

Hey Zanne,

I read the slope should be 1/4" slope per foot also. It makes sense, since gas has water vapor within it, that can condense, especially when the vapor or gas is warmer than the pipe surrounding it. I bet this problem will be more pronounced once it becomes cold outside (and in the attic) as the condensed vapor will just sit in the horizontal pipe, instead of draining down and out the main drain.

I will wait until I can withstand the attic temps and place a slope on the vent pipe. If nothing else, it will not make the problem any worse than it currently is.

If you think of anything else, please let me know. I appreciate your help on this.

Heater

Hmm.. I'm wondering about the horizontal line as well. I could be wrong, but once it goes beyond the initial 6 inches above the flood level, I don't know if the angle really matters too much since it isn't like water-- but then, air is affected by gravity as well, so it might just be sitting in there.. I really don't know. I'm hoping someone will answer this.

I looked it up and from what I've read, the vent needs to slope 1/4-inch per foot upward away from the fixture.

Still hoping someone who actually knows about this stuff can answer though.

 

[phishfood]

We offset vents horizontally all of the time, and sometimes for quite a distance. There are overall distance limitations on the allowable length of a vent, but you won't really run into problems with that in a house.

International Plumbing Code does not specify a particular slope that a vent must have, just that it be graded to drain back to a drain. This is so that water from condensation will not fill up the vent and block it off. It is not necessary to have 1/4" per foot slope on a vent.

For your vent to be blocked off completely with water over a 14' distance, you would have to have more than 1/8" per foot of backfall. I am not saying completely rule out lack of slope on a vent being the problem, but I tend to be skeptical of that theory.

Can you get a picture of how the fixtures are venting?

 

[Zanne]

I think adjusting the slope is a good idea if you can manage it. I feel you on the not wanting to go into the attic thing. Nobody has gone into my attic in years and I don't even want to know what is up there. I sometimes hear things crawling around.
I need to look it up, but there are some sites where you can find the building code information for your area (usually by state) and there should be links with .pdf files that have detailed info on what sort of venting is proper and such.

I looked up my state's info and think it was something like 2 thousand pages long (or close to it) and kept referencing previously mentioned rules and was a jumbled mess. I wish they had these things in laymen's terms.

I recently read something that said the toilet should be within 5 feet of the vent stack.

I'm hoping that adjusting the slope of the vent pipe will help your situation.

 

[heater963]

Hi phishfood,

I can only describe how they are venting, as the vent line is in the wall. The vent line is a 2" line that appears to be "T" (eed) behind the sink. That vent line has a 90 elbow on it about 4" above the sinks overflow drain and travels about 3 feet or so horizontally to the toilet. Above the toilet the vent line, picks up the toilet vent and the shower/tub vent. It travels thru the ceiling, has another 90 elbow on it and travels 14 feet horizontal across the attic. It has another 90 elbow after the 14 foot run and goes vertical thru the roof. They did this horizontal run to place the vent stack on the backside of the roof to hide the vent from view.

I was researching last night and found a website that stated the P trap must be a minimum of 2" from the top of the "crown weir" to the "top of the dip" and a maximum of 4". I measured my current P trap and it is approx. 11/4".

What I believe is happening is when we turn on the water faucet at the sink, the draining water is pushing water out of the P trap. This is creating an "air gap" that allows sewer gas to come in thru the sink drain. Once we turn the faucet off, the trap refills and reseals, keeping the gas at bay.

Would a deeper P trap be a good place to start? They also transitioned from the sinks 11/2" drain line to a 2" drain that runs to the main 3" drain. Their "transition" is a hodge-podge of fittings that ultimately have the sink drain composed of various slip joints at an angle to the 2" drain. I looked at the kitchen sink drain and the P trap is deeper and goes straight into the 2" drain line. The bathrm sink drain is level, but whoever put it together was either high, not a plumber or perhaps both. All 3 bathroom sinks have shallow P traps and all 3 have the same problem, despite being on separate vent lines. The additional two sinks, on the other side of the house, vent straight vertical thru the roof. They drain fine, but displace the water seal when water is turned on, creating what appears to be an air gap for that nasty gas to come in via the sink drains. Turn the water off, trap refills with water and water seals the gas out until the sink is used again. ( It seems like the vent pressure is there, but takes a few seconds to create a positive pressure strong enough to stop the gas from entering the sink drains. (That "few seconds" smells terrible.)

A penny for your thoughts on this.

Thanks much,

Heater

 

[heater963]

Hi Zanne,

Appreciate your time on this.

I think I have figured out what is actually occurring. When we turn the water faucet on, the water goes down the 11/2" drain to the P trap. It displaces the water in the P trap and that allows septic gas to enter the house, via the bathroom sink. Once we turn the water off the P trap reseals, creating a water seal and stopping the gas from coming up the sink drain.

I think the vent pressure is present, but it appears to take a few seconds before it creates enough pressure to push the gas back down the main drain direction. I was researching last night and read that a P trap should have a minimum 2" depth from the "crown weir to the top of the dip." I measured my P traps and found the depth they are speaking of is a mere 11/4." The "minimum" is 2" and the maximum is 4" so my P traps are definitely a bit shallow. I was entertaining a deeper P trap, which I think may provide an additional few seconds when draining the sink(s) for the vent pressure to come in and do what it is supposed to do...create a higher pressure than the gas can...pushing the gas back to the main drain, instead of up the sink drain. Obviously, the few seconds when the gas comes out of the sink drain is due to a "negative pressure" (vacum) at the sink drain outlet into the house. It appears the vent line eventually creates atmospheric pressure and pushes the gas back towards the main drain. That few second "lag time" is very smelly and unhealthy. I was contemplating a deeper P trap, as this may buy the precious few seconds I seem to need to stop this problem.

Have you ever heard of such a thing? I know they transitioned from the 1/1/2" sink drain to a 2" drain that feeds into the 3" main drain. That "transition" is hodge-podge of fittings, but is level to the 2" drain. Whoever did the plumbing was no plumber, high on drugs or perhaps both.

The vent system appears to be working, as the drains are ALL draining without issue(s), whereas, if the venting were an issue, I suspect the drainage would be making noises or minimally draining very slowly.

Thanks again for your help. Do you think a deeper P trap may solve this problem, as the volume of water in the P trap will be more than existing and when it does drain will therefore push more gas down the drain, instead of allowing it up and into the house. The increased volume of water may also create more of a draw or suction on the atmospheric vent line, creating the pressure needed to overcome the "vacum" of the sink opening into the house.

Again, I am no plumber, but to me, this "theory" seems plausible.

Thanks very much,

Heater

 

[Zanne]

heater963, thanks for the info on the P-traps. I didn't know that. About all I know is that they need to stay wet and that an S trap should not be under a kitchen sink. LOL.

I know what a weir is but I wonder what a "crown weir" is. Is it the same as a trap weir?

I wish that I had more information for you. Maybe if you can extend the length so that the P-trap is the right distance you can see if that does anything.

I don't think going from a smaller to a larger opening for a drain would be a problem, but I'm no plumber.

Do you have a picture of the "hodge podge"?

I know that feeling of thinking whoever did some work did not know what they were doing.

I hope that you are right about the P-trap and that you can resolve it easily.

 

[heater963]

Hey Zanne,

I got it! It was a combination of overflows clogged up with crud and P traps that were too shallow. I cleaned the overflows out on all of the sinks and installed a deeper P trap on one of them initially. The deeper P trap did teh trick. I changed the other two sinks out the next day and BINGO the sewage gas smell is gone.

Thanks very much for your time and assistance. What an "easy fix" that in the end makes complete sense as to why what was occurring was.

Thanks again.

Heater

heater963, thanks for the info on the P-traps. I didn't know that. About all I know is that they need to stay wet and that an S trap should not be under a kitchen sink. LOL.

I know what a weir is but I wonder what a "crown weir" is. Is it the same as a trap weir?

I wish that I had more information for you. Maybe if you can extend the length so that the P-trap is the right distance you can see if that does anything.

I don't think going from a smaller to a larger opening for a drain would be a problem, but I'm no plumber.

Do you have a picture of the "hodge podge"?

I know that feeling of thinking whoever did some work did not know what they were doing.

I hope that you are right about the P-trap and that you can resolve it easily.

 

[IFIXH20]

Hi Zanne,

Appreciate your time on this.

I think I have figured out what is actually occurring. When we turn the water faucet on, the water goes down the 11/2" drain to the P trap. It displaces the water in the P trap and that allows septic gas to enter the house, via the bathroom sink. Once we turn the water off the P trap reseals, creating a water seal and stopping the gas from coming up the sink drain.

I think the vent pressure is present, but it appears to take a few seconds before it creates enough pressure to push the gas back down the main drain direction. I was researching last night and read that a P trap should have a minimum 2" depth from the "crown weir to the top of the dip." I measured my P traps and found the depth they are speaking of is a mere 11/4." The "minimum" is 2" and the maximum is 4" so my P traps are definitely a bit shallow. I was entertaining a deeper P trap, which I think may provide an additional few seconds when draining the sink(s) for the vent pressure to come in and do what it is supposed to do...create a higher pressure than the gas can...pushing the gas back to the main drain, instead of up the sink drain. Obviously, the few seconds when the gas comes out of the sink drain is due to a "negative pressure" (vacum) at the sink drain outlet into the house. It appears the vent line eventually creates atmospheric pressure and pushes the gas back towards the main drain. That few second "lag time" is very smelly and unhealthy. I was contemplating a deeper P trap, as this may buy the precious few seconds I seem to need to stop this problem.

Have you ever heard of such a thing? I know they transitioned from the 1/1/2" sink drain to a 2" drain that feeds into the 3" main drain. That "transition" is hodge-podge of fittings, but is level to the 2" drain. Whoever did the plumbing was no plumber, high on drugs or perhaps both.

The vent system appears to be working, as the drains are ALL draining without issue(s), whereas, if the venting were an issue, I suspect the drainage would be making noises or minimally draining very slowly.

Thanks again for your help. Do you think a deeper P trap may solve this problem, as the volume of water in the P trap will be more than existing and when it does drain will therefore push more gas down the drain, instead of allowing it up and into the house. The increased volume of water may also create more of a draw or suction on the atmospheric vent line, creating the pressure needed to overcome the "vacum" of the sink opening into the house.

Again, I am no plumber, but to me, this "theory" seems plausible.

Thanks very much,

Heater

The 2''- 4'' is the amount of water that should be in the trap to create the trap seal. There should be a min 2'' and a max of 4'' of water in a p-trap. Although you measured a 1 1/4'' on the outside of the trap the water in the trap is at least (should be) 2'' deep. I have ran into a couple of lav sinks where the smell was in the overflow. The smell was more noticeable when the water was running or just after uses.

 

[heater963]

One sink is still a problem. I thought I had conquered this problem, but over the weekend noticed the smell was back in one of three sinks, that is on a separate vent. I know the vent is good, because the sink, toilet and tub all drain great without any noise.

I have no idea what is wrong. It does occur when the water is initially turned on and comes out the sink overflow.

 

[phishfood]

My bet is that there is still some crud in the overflow.

 

[IFIXH20]

Go to the hardware store or big box store and get a 1 1/4'' tubular fernco coupling and a 3/4'' pvc cap. Remove the p-trap from the sink in question. Place 3/4'' pvc cap in one end of fernco coupling and tighten clamp, now attach the other end of fernco coupling to the pop-up tail piece ( the drain that is attach to the sink) do not over tighten fernco on tail piece causing damage. Once fernco coupling is in place put a little water in sink to see if any leaks from fernco coupling. If no leaks is present pour a 1/2 cup of vinegar in sink and fill sink with water pass the overflow hole - let water/vinegar solution set overnight. Place a bucket under drain for safety. Place a rag in open trap arm to hold back the sewer gas. Do not close sink stopper during the process.