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 how to locate vent line that does not extend thru roof
Author: koecher (TX)

I have a septic tank drain system, the old style with drain fields.

I am getting sewer gas in one portion of the house when we get real heavy rain that leaves standing water in the yard which I am sure is flooding the septic system.

My guess is the sewer gas is entering the house through a vent line that was not run up thru the roof. This only happens when there are real heavy rains.

It sewer gas is entering the house in a utility room that adjoins a small bathroom. The utility room has a washing machine drain and the tiny bathroom has toilet and sink only.

The utility room and bathroom each have an exterior wall which makes it easy to look from the outside for a vent pipe thru the roof above either room. No vent anywhere.

There are no problems with toilet flushing or sink or washing machine draining so there is venting, it just is behind the wall.

I want to find the open vent to fix the problem correctly but do not want to remove any more dry wall to find and fix than I have too.

Any suggestions on locating the open vent. Thanks.

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 Re: how to locate vent line that does not extend thru roof
Author: packy (MA)

"There are no problems with toilet flushing or sink or washing machine draining so there is venting, it just is behind the wall"
.............................................
you don't know that. the problem could that there is no vent and you are losing the trap seal in the washing machine trap or the sink trap.
I don't want to sound like a smarty but wouldn't it be nice if we could see behind walls and ceilings. sadly the only way I can think of would be to send a sewer camera up a cleanout and hope it finds its way to the vent.

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 Re: how to locate vent line that does not extend thru roof
Author: hj (AZ)

And WHAT would a "sewer camera" show him? He needs a sonde that can be traced, assuming there is ANYWHERE it could be inserted so it would go upwards. Otherwise he has to get into the attic, assuming there is one and look for the a pipe(s).

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 Re: how to locate vent line that does not extend thru roof
Author: bernabeu (SC)

or a bore scope

today we would use a 'flexible' shaft video camera w/ built in monitor to look into the wall

however, with exterior wall insulation ?

[www.bing.com]



================================================

Retired U.A. Local 1 & Local 638 ~ Measure Twice & Cut Once ~



Edited 1 times.

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 Re: how to locate vent line that does not extend thru roof
Author: sum (FL)

I wonder if an infrared camera may be useful.

It works by showing temperature differentials. So an air leak or water leak pops up. A vent pipe? I don't know.

I was at a Home Depot and they have that in the rental department. I think it was $45 or $75 for a daily rental I don't remember now. The guy let me borrowed it for 5 minutes walking around the rental area and it was pretty impressive.



Can you get the vent pipe warmer by running hot water down the drain?

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 Re: how to locate vent line that does not extend thru roof
Author: m & m (MD)

Try replacing the toilet wax seal first; it could be leaking gas when there is positive pressure on it during heavy rains.

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 Re: how to locate vent line that does not extend thru roof
Author: koecher (TX)

you are absolutely right, I am assuming there is a open vent behind the wall because I can not see any vent pipe going thru the roof in the area of the bathroom/utility room.

More correctly, the drain system is venting itself in that part of the house and I do not know how. Maybe a vent was not even put in as someone suggested and the drain system is venting thru one of the drains, i.e. the washing machine or sink or toilet.

The washing machine drain can be ruled out because the discharge hose is shaped like a pee trap and has water in it when machine is not in use. The sink is trapped so I don't think it can be either of them.

This leaves the toilet. Someone said maybe a leaking wax toilet ring. I don't know about that. The toilet does not leak water when flushed.

If not the toilet, washing machine or sink, I am back where I started assuming an open vent pipe behind the wall.

I was hoping some plumbing guru would have a good idea how to go about locating the source. After reading the replies, I can try a new wax ring and if that does not solve the problem, I guess I am looking at removing a lot of dry wall to expose from above where the washing machine drain pipe goes into the wall back and around to where the sink drain goes thru the wall to look for a vertical pipe from the waste drain pipe.

There has to be a better way but maybe not. Plumbing gurus speak up.

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 Re: how to locate vent line that does not extend thru roof
Author: hj (AZ)

From what you are saying, I have to assume this is a flat roofed house without an attic.

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 Re: how to locate vent line that does not extend thru roof
Author: koecher (TX)

no. it is a gabled roof but has a half story above the ground level running down the middle of the house leaving a tiny attic space maybe 3 feet high by maybe 5 foot across to soffit area over the utility room and bathroom.

This attic space is accessible thru an opening in the upper level bedroom wall I made long ago to add a run of AC ductwork to add an AC vent at the far end of the bedroom.

I will look this evening to see whether there are any vertical pipes visible in the attic area but am pretty sure there are none.

If the vent was located that high, the sewer gas would be bad upstairs which it is not. It is only in the utility room area.

What I cannot understand is if the vent wherever it is, is not directly into the utility room area, then why is the sewer gas so strong in there.

Since this is a problem that only happens ever so often, it has been relatively easy to ignore until here recently when we have been having a lot of rain.

I have decided to address the problem even if it means cutting a bunch of sheet rock out. However, before I undertook this extreme measure, I wanted to make sure there was not a less destructive way to accomplish this.

There should be a vent pipe exiting the roof above the bathroom area for the sink and toilet which there is not. There is also venting occurring somehow somewhere in the utility room area which is open and unobstructed or there would be water flow/flush problems when running the sink or flushing the toilet which there are not.

A leaking toilet wax ring which allowed that much air to enter would make noise and leak water.

If I can locate the vent, I can solve the problem.

Thanks for giving my problem some thought. new minds come up with new ideas.

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 Re: how to locate vent line that does not extend thru roof
Author: hj (AZ)

quote; If I can locate the vent, I can solve the problem.

OR at least you will eliminate one possibility, but there could be MANY others.

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 Re: how to locate vent line that does not extend thru roof
Author: m & m (MD)

Your problem is one that cannot be diagnosed without "boots on the ground".

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 Re: how to locate vent line that does not extend thru roof
Author: SwimRunPlumb (MI)

I agree that the toilet seals should be checked first. The seal on toilets can leak sewer gas without leaking water. This is much more likely than a random vent in a wall that did not get stubbed out. I would lay down a very hefty wager that it is NOT some "forgotten" about vent in a wall.

Sewer gas leaks in the house on septic tanks are a very common thing, and the heavy rains always make it much more noticeable. Unfortunately it is not an easy thing to diagnose. You may want to try peppermint or smoke.

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 Re: how to locate vent line that does not extend thru roof
Author: hi (TX)

Koecher,
You may want to verify what the status of your leach field is.. if you have standing water that may represent failure of the leach field. This will not cause sewer gas problems but could be a major problem for u. Hopefully, each leg of the leach field has an inspection port on it to use ur scope or other inspection methods ie direct inspection by digging up a portion of the line.

[www.youtube.com]

I really like chambers. They have much more capacity than the older perforated pipe system. I also like dual fields and switching the leach field twice yearly to prevent saturation
[inspectapedia.com]

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 Re: how to locate vent line that does not extend thru roof
Author: sum (FL)

This reminds me of one episode where I was smelling sewer gas in a room in a building years ago.

No other room has this strong odor. No one can figure out why, no where does the sewer line even come close to this room.

Other rooms and offices you can smell a little, but nothing as strong as in that one single room.

After a lot of investigation, hiring plumbers, leak detection experts etc...finally they figured it out.

Some AC tech decided to drain the AC condensate line into the sewer instead of running it outside the building. He cut through the vent line to put in a branch tee. He did not put a trap on that tee, just an upward elbow and went up to the floor above. That was a 2" line and it goes went up through the floor into the sanitary closet where the AC unit is. The AC pipe just ended there. The 1" AC condensate line was ran to that spot, and just openly inserted into that 2" line. Sewer gas was in that room, and when the AC turns on, it sucks the air from that room, partially filled with sewer gas.

Now they kept the offices REAL cold. Some of the employees had to bring in sweaters even though it's 90 degree out in Miami. Many of them just got up on their desks and slid their vents closed. Except one GUY. He did not close his vent for the AC, and he is the one getting all the sewer gas pumped into his room.

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 Re: how to locate vent line that does not extend thru roof
Author: hj (AZ)

It makes no difference whether there was a trap on it or not, because in low humidity periods the trap would dry out and still suck sewer gases. That is why ALL knowledgeable AC installers run the drain to the exterior of the building or into a sink trap which will always have water in the trap under normal usage.

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 Re: how to locate vent line that does not extend thru roof
Author: sum (FL)

OK but hj there is no period of low humidity in Miami. It's either 110% or 95% B) B) B) .

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 Re: how to locate vent line that does not extend thru roof
Author: hj (AZ)

In the winter, without the A/C operating, there is no condensation to keep the trap full, so it would still dry out and cause the odors. It is NEVER a good idea to connect it directly to the sanitary system, with or without at trap. Which is why I said "knowledgeable A/C installers NEVER do it". Hacks and handymen do do it however.

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 Re: how to locate vent line that does not extend thru roof
Author: sum (FL)

I understand your point hj, but in my case where the office were getting sewer gas, it wasn't the presence or absence of water in the trap.

First the trap isn't there.

But even if it was, it wouldn't make a difference. Between the AC tech ran the 2" pipe up and then he terminated the 2" pipe in the janitor's closet openly. Then he ran the 1" AC condensate line to it and inserted it into the OPEN 2" pipe, no transition coupling, nothing. So there was this open space between the ID of the 2" and the OD of the 1" where sewer gas was just pouring out. If you just look at it from inside the janitor's closet you would have assumed it's a badly made floor drain. It's unreal.

But yes I understand where you are coming from, what's amazing is that I was at a friend's house and they had the overflow pan connected to a sewer drain. Not even the condensate line which will drip water when the system is on, but the overflow pan they had a weir that drains into a 3/4" pipe that runs to the sewer line. It's weird to see two 3/4" lines connected to the sewer, one from the AC condensate line, one from the overflow pan. That overflow pan is always dry unless there is a problem and sewer gas's been going into his attic.

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 Re: how to locate vent line that does not extend thru roof
Author: koecher (TX)

update: I was suspicious of washing machine drain because no washing machine box built into wall with spot for supply valves and drain hose but just piece of 1' pvc sticking thru sheetrock to clamp drain hose onto. Both water supply lines stick thru the sheetrock same way.

I have been planning to redo this correctly for some time but it was one of those projects hard to get motivated to do. Anyway, last night I cut a window in the sheet rock above where the drain line goes thru from stud to stud and maybe 10 inches from top to bottom which encompasses the washing machine drain line and both water supply lines. I removed it and looked into the wall to see where the wild goose, I mean, where the drain pipe goes and to look for other plumbing like maybe a open vent pipe. Observations:
1.no insulation in wall(exterior) between these two studs;
2.drain line not trapped;
3.no vent pipe any where in this area;
4.drain pipe looks like 2inch white pvc that goes straight down but hard to say where, maybe thru the slab or maybe into a coupling of a black horizontal run of pipe.

The view is obstructed but photos taken with my cell phone show the CDX sheeting around the drain pipe at slab level to be stained blackish like inside of septic tank. Maybe I have a leak here? plywood should look like brown wood, not black.

I wonder if there is a leak here and this is the source of the sewer gas?

I plan to extend the sheetrock cutout down to the slab this evening so I can see exactly what is going on here. It don't look good.

The vent source is still not located unless sucking air thru leaking area which it probably does but I doubt is the real source of the venting. It may such air there now but once upon a time we did not have this sewer gas problem.

I have a roof vent in the kitchen over the sink which adjoins the utility room. Maybe a horizontal run of vent pipe from this vent pipe tying into drain pipe somewhere in utility room? Still have not examined the sink drain.

I will report tomorrow what I find. So far no brown trout. (:

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