Septic gas belching past full p-traps/ Septic tank drainfield failing? Venting issue?

[Jadnashua]

30' is at least 7.5" drop required. That drop has to be continuous...no flat spots or back slope. More is okay.

 

[Leejosepho]

I had somehow envisioned must less than 30' of troubled line, but yes, that sagging "belly" Redwood has described is your problem. One of my own lines has the same "burp" symptom you are experiencing, but my problem stems from a buildup of solids in my tank that are plugging my outlet filter and backing things up a little way into the inlet line. I will be having my tanks pumped later this week.

1/4" per foot is an ideal slope, but 1" in 10' can be an acceptable minimum. If a camera can locate your low spot and that spot happens to be close to the outside of the house, maybe you or someone can carefully dig in a little way and remove enough droop to allow that line to vent.

Keep your head out from under the house and keep us posted, eh?!

 

[Sponsor]

 

[Redwood]

Usually even if the sag is not the whole distance there is considerably longer trenching to allow repair than the actual sag...

1/4" per foot is code legal everywhere... (2 1/2" per 10')
1/8" per foot is allowed under some codes in some conditions... (1 1/4" per 10')

1" in 10' is not allowed!

 

[Leejosepho]

1" in 10' is not allowed!

Whether or not it is "allowed", 1" in 10' can be an acceptable mechanical mimimum if the line is straight and well-bedded. At least in part, steeper slopes are "required" to cover installed sags and/or eventual settling. I have one line (about 10' long) that was set at only a mere 1/4" in 4' several years ago, and it is still just as clean on the inside as on the day it was installed. A few months ago, I was shocked to learn storm drains are often set at far less than even that, but those lines usually experience long and heavy flows in comparison to the flush of a toilet.

 

[Redwood]

Whether or not it is "allowed", 1" in 10' can be an acceptable mechanical mimimum if the line is straight and well-bedded. At least in part, steeper slopes are "required" to cover installed sags and/or eventual settling. I have one line (about 10' long) that was set at only a mere 1/4" in 4' several years ago, and it is still just as clean on the inside as on the day it was installed. A few months ago, I was shocked to learn storm drains are often set at far less than even that, but those lines usually experience long and heavy flows in comparison to the flush of a toilet.

I suppose a backpitched line is okay too as long as it works...

The thing is Lee that the code specifies things for a reason.
In this case it is maximum reliability under use conditions & health of the building occupants...
I mean what's wrong with a little fart gas belching out of a line?
Heck, it works!
Thats why the code is good enough for plumbers and building inspectors, and good enough is good enough for handymen...

 

[Ladiesman271]

Just wondering how "sewer gas" can backup into a house if every fixture is trapped and vented properlY?

 

[Redwood]

The line flooding due to the back pitch prevents proper operation of vents. Also there is no doubt that there are some things that are not properly vented... Like a few s-traps...
They love to pop in this circumstance...

 

[Ladiesman271]

The OP said this:

"The lower bath (where gas odor is worst from sink) is the last stop on the main waste line that runs out towards septic system. I removed the toilet (the very last fixture draining into the waste line before heading out towards the septic tank.) I had someone run water from the kitchen sink (main level of house) and a massive amount of gas was emitted from the toilet pipe (as waste water ran down main stack and down towards this line on its way towards septic tank.)"


If the main line was flooded, I assume that he would be able to see the level of the liquids in that basement toilet drain pipe when the toilet was removed. Am I wrong about this?

 

[Redwood]

Picture this...
The last sink on the line being s-trapped...
A big slug of water flying down the pipe heading for the tank...

In between that slug of water and a section of flooded pipe is this little tiny s-trap...

Pop!
I have seen trap water hit the ceiling in this circumstance.

Wanna see something really wild?
Have a pressure assisted toilet spray into this line!

 

[Leejosepho]

If the main line was flooded, I assume that he would be able to see the level of the liquids in that basement toilet drain pipe when the toilet was removed. Am I wrong about this?

No, and here is what he had said:

When we uncovered the tank fully this time, the backhoe operator and my father immediately noticed that the line running into the tank was angling slightly upward into the tank ...
We did flush an upstairs toilet a few times to see what was happening and it did appear some minor solids were getting hung up in water the main line. Nobody thought that this water standing in the pipe would be enough to cause any problem.

The error there was simply in not realizing some part of the line is sagging and remaining full ... and that means anything dumped into the line between the sag and any vent farther upstream can create pressure that must be released somewhere.

Redwood: You are saying things I did not even come close to saying or to even thinking about merely implying. What we have here is a situation where just about any fall gained at all could be sufficient for avoiding a very expensive repair. "Codes" are not mechanical absolutes without which nothing at all would ever function.

 

[Redwood]

Redwood: You are saying things I did not even come close to saying or to even thinking about merely implying. What we have here is a situation where just about any fall gained at all could be sufficient for avoiding a very expensive repair. "Codes" are not mechanical absolutes without which nothing at all would ever function.

Lee, Your proposed pitch while it may eventually drain dry would prove to be problematic. It's really plan and simple...

The code is what we plumb to because it works!

If your proposed pitch was acceptable then the code would mearly specify that a drain could not be dead level. Lines with less than the allowed pitch are not reliable and tend to have a very heavy sludge build up as the lack the velocity to scour the pipe.

 

[Leejosepho]

If your proposed pitch was acceptable then the code would mearly specify ...

I did not propose a pitch, and I have not been talking about any code.

 

[Redwood]

1/4" per foot is an ideal slope, but 1" in 10' can be an acceptable minimum.

There is no such thing as a acceptable minimum less than the specification of the code. It's that simple and not worthy of further debate!

 

[Leejosepho]

There is no such thing as a acceptable minimum less than the specification of the code.

So then, the OP should either immediately spend whatever it costs to re-slope the line in question or lose his CO?

I cannot imagine any inspector being that unreasonable.

 

[Redwood]

No Lee,
He needs to correct the pitch problem if possible.
If correct pitch is not possible then alternative methods can be used...
Plumbers know these things...

 

[popdisplay]

I have a similar problem
First a few details about my system
my first tank is divided in half
It feeds a motorized pump (2nd) tank which moves water to my leach field.
This is a lake home which sees at most 100 days of use each year. 80 of those days are inhabited by 2 people only. We had the tanks pumped out 2 years ago.

Whenever we have a large gathering of people, like clockwork, the lower level stinks of sewer gas- which makes it's way up stairs.

I checked the tanks and they all appear normal. Nothing is overflowing. The area around the tanks is dry. The smell is stronger in the lower level of the house than the area around the tanks- but the area around the tanks does smell bad.

All of the sinks, showers, tubs, toilets drain properly. We looked at the roof vents and they appear to be unobstructed.

A number of so called septic experts can't solve the problem.

Can anybody here lend a hand? I'll be happy to answer all questions.

 

[Mikey]

I have a similar "pump to gravity" system, but no smell. If you're sure the pump is working OK, I'd have the tanks pumped and see what happens. If the smell goes away for a while, then there's a problem downstream - clogged line to the D-box, clogged D-box, failed leach field, etc. The next step would be to run a camera down the line to check for crimps, roots and clogs. If that's OK, then dig up the D-box and have look at that. Ultimately you rebuild or relocate the leach field. Fixing the problem gets more difficult (and more expensive) the farther downstream you get; I would hope for a problem in the line from the pump tank. Theoretically it carries liquid effluent only, so often the installer tries to save a few bucks and use a cheap, small-diameter black poly pipe, which can be prone to failure over time.

 

[Mikey]

Coincidentally, a friend just had his septic line back up into his house, which is a much more serious problem than a smell. The culprit appears to be a bad clog in the line from the house to the first tank - about 8 feet. Digging a little deeper (no pun intended), it looks like there's a problem with the design or construction of the inlet baffle in the first (settling) tank, which abets the clogging of that area with toilet paper. Further complicating the immediate inspection of all this is - someone built a sidewalk over the line and the inlet of the tank. The real culprit, though, could be the toilet paper itself, which is labelled as "septic safe" but it's the thick, fluffy, squeezable kind, which is certainly not "septic friendly". A big-enough wad of this TP apparently will build a small clog, but it won't dissolve away in time to prevent a larger clog buildup. That's speculation, mostly, but I'm sticking with it for now.

 

[Marioz123]

Split level house in the country--approximately 30 years old
Septic system--1500 gallon tank
I've lived in house while renovating for about 2 years. My parents owned it previously. House was unoccupied for approximately 5 years to me moving in and renovating.

First noticed very strong septic gas smell from lower level bath vanity (vessel bowl.) Happens only when water is run and gas immediately breaks or "belches" past p-trap seal. This is where the worst gas problem occurs.

Later noticed this was happening in kitchen sink on main level of house. Gas is not as strong, but still very evident.

Finally checked main bath on upper level (two basins on vanity) and smell is very faint. Same belching condition.

There is no siphoning of water from p-traps. Bubbles "belch" through p-trap when water is run from fixture and runs into drain.

The home never previously had problem to my knowledge prior to the 5-year period house sat unoccupied. My parents lived here and I grew up in the home. The original homeowner (who my parents purchased house from in early 1980's) also built the home primarily himself. While most construction was outstanding, I question his understanding of plumbing. None of the individual fixtures in house have their own vent branch into the main stack with the exception of the kitchen sink, which actually has its own vent (through roof.) The main stack actually serves as a long wet vent into which most of the waste lines drain into. Neither vent through the roof is clogged...they have both had a hose run down and verified water runs freely through. In the crawlspace below the kitchen I opened a cleanout which is directly below the sink and water from the kitchen sink vent was very visibly running clean through.

I had a plumber out. He had no answers other than "most fixtures were not properly vented." He could not explain why kitchen sink emitted the gas because it did seem to be vented.

But wait, there's more: I had the septic tank pumped about 3 months ago. I learned later that the tank probably had 3 access points (1500-gallon concrete tank) but we only dug down to the center. Therefore, the inlet and outlet were not inspected. This was the first time in 30 years the tank was pumped. The "pumper" said that it seemed surprisingly not overfilled with solids. Additives like Rid-X were used throughout the years, including recently.

This septic tank is buried right behind the home, and to my knowledge is attached to the usual drainfield. However, one unique (and probably unlawful) feature is that several hundred feet away in a small primarily dry creek an overflow pipe peeks out which I'm told is an overflow from the septic system. When excessive rains came, it was uncapped to provide a release point for an apparently overtaxed drainfield. This has been uncapped since I've lived here (2 years) and probably a number of years prior. There doesn't appear to be much dampness coming from it, however I haven't tested it by running massive amounts of water in the tank and seeing if there is any "overflow" from this drainpipe.

The lower bath (where gas odor is worst from sink) is the last stop on the main waste line that runs out towards septic system. I removed the toilet (the very last fixture draining into the waste line before heading out towards the septic tank.) I had someone run water from the kitchen sink (main level of house) and a massive amount of gas was emitted from the toilet pipe (as waste water ran down main stack and down towards this line on its way towards septic tank.)

So...barbaric septic gas seems to be creeping up into the main stack and the various waste lines to fixtures, and most of the sink p-traps appear to fail to keep it in check.

As I mentioned, this was not problem in the past to my knowledge. Therefore, although I recognize the system is not properly vented, why did it become a problem at some point? The septic odor is unbelievably rank. By the way, I worked as a licensed embalmer for a number of years, so I know a bad smell when I'm exposed to it!

Could the septic drainfield be failing/clogged to some extent and not absorbing gases? There has been no problem with waste water backing up.

Obviously it's as if the gas is trapped throughout the stack and doesn't fully release through the roof vent(s).

Anyone? Anyone?

Many thanks in advance. I'd be glad to answer any specific follow up questions. I'm starting to lose sleep over this after having nightmares about trying to re-vent the system, only to learn the septic tank (drainfield) is the culprit. Or how about vice versa? Either way, I know I'm talking about a decent sized investment to rectify this.

Ryan100...seeing as your post is a decade and a half old, this is kind of a shot in the dark but I figured what the heck. You're describing my current situation to a T. Like down to plumbers coming and just saying things aren't properly vented or suggesting my traps are dried out (they're not) and otherwise offering no tangible solutions. Also had my tank pumped hoping it would fix the problem, but no luck, if anything it got slightly worse.

Can I ask what ultimately wound up solving your septic smell problems? I'm at a total loss.

 

[Tuttles Revenge]

Get a camera w/ recording down the line to inspect it. Likely a clog or belly causing a loss of cross flow of air.