Septic odors in the house


  #1  
Old 07-04-16, 12:58 PM
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Septic odors in the house

We live in Mexico. This is the first house we have lived in with a septic system. I don't know much about our system nor how septic system work in general. We are in this house almost 3 years. Every year when we enter rainy season (now) funky odors come from the floor vents in the master bath.

In the farthest corner of our lot, along a retaining wall is a 3" PVC tube which I believe is the vent for the septic system. It is just normal PVC with no cap. When it rains here - almost every night - it can rain 2-3". I'm wondering if the PVC tube - which raises perhaps 15 feet or so from the ground - has gotten filled with water and therefore there is no venting (except into the house). Does that make sense ?

I was thinking of drilling a small hole in the pipe to see if water leaked out to confirm my theory. Then if I'm correct I was thinking of adding some sort of cap to the PVC pipe.

Any thoughts appreciated.

Edit : btw - I have never done _anything_ in terms of septic maintenance. Never added chemicals etc. When we bought the house the previous owners gave us some architectural docs for the house - including the septic system (which I think was called a septic 'farm'). I believe (from memory) there is no metal or plastic 'tank'. There is a bunch of underground rocks - with no way to access anything without starting to dig.
 

Last edited by lhpdiver; 07-04-16 at 01:16 PM.
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Old 07-04-16, 03:02 PM
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Are you certain you have a septic system? Cesspools and leach pits are common and sometimes located underneath homes.

Most septic tanks and leach fields do not have vents. A pipe sticking up 15 feet is unusual but it could be a vent. If it is a vent and connected to your septic system it will not be full of water. What makes you think that it might be full of water?
 
  #3  
Old 07-05-16, 09:57 AM
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Normally the floor vents are connected to ducts. Ideally the ducts are airtight but in practice they are not quite.

Properly, all the drain pipes and the septic tank form a sealed system within the house. Vent pipes here and there rise up above roof level. Water filled traps under each plumbing fixture seal off the inside of the drain pipes from the house air.

Properly, a septic tank or even a cesspool is not full of rocks. The space inside is needed to accumulate non-bio-degradable sludge in.

If for some reason, such as leaks or cracks or rusted out components, the inside of the drain pipes have some connection to shared air space with the insides of the vent ducts, then odors can get into the house.
 
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Old 07-05-16, 10:41 AM
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Thank you both for your replies. Took me a while to track down the schematic of our septic system - which I'm looking at now.

Our 'system' is a series of compartments - there is no 'tank'. The system is approx. 2 meters tall and sits completely underground - a good distance from the house. The system is enclosed in brick. Waste enters on one side and somehow flows into a 'fermentation' chamber. Next it goes to an 'oxidation' chamber - which has the one and only vent - the 15' tall 3" PVC tube. It is the oxidation chamber which looks to have rocks depicted.

There are no vents on top of the house for this system. Our house is a very well made house - built by a Swiss guy 20 some years ago. Last year or so - when we last had these odors - someone said our drains in the bathroom needed to be extended into water forming a seal of sorts. I kind of did that by purchasing a cheap gizmo that extended lower and allowed water to drop but not rise.

I'm pretty sure our problem is related to the recent rainfall.
 
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Old 07-05-16, 11:46 AM
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If you do not have traps (the low spots with water) on every fixture you can have sewer gas flow back into the house.
 
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Old 07-05-16, 12:07 PM
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The only room we have a problem with is one large bathroom - which is really two rooms - with a door between them. That is also the room closest to the septic system. One room has a big tub, shower and toilet. There are two drains; one in the shower, the other in the middle of the room. The other room has two sinks. The sinks have traps.

The floor drains are conical and I believe are supposed to dip into water. In fact I vaguely remember someone saying we need to regularly add water to the drains to form the seal. It is just odd that we only have this odor problem during the 3 months of rainy season. Which is why I was thinking of that exposed 15' tall PVC tube.
 
  #7  
Old 07-06-16, 08:22 PM
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If you add water to the shower drain and floor drain twice a day, would the odors stop?

If a trap leaks dry then the seal is lost and odors will enter the house. If the floor drain trap (below floor level) leaks dry, you won't see that and all you could do is jump to conclusions that the odors are coming through because that trap went dry. Or maybe a drain pipe just somehow broke somewhere in the middle and that's why you are getting odors.

The "fermentation chamber" would correspond to a septic tank proper in the U.S. The "oxidation chamber" corresponds to a tank after the septic tank in newer U.S. systems in which there is an electric pump to aerate the liquid. The liquid must dissipate somewhere which can either be a leach field or the oxidation chamber's being porous (seepage pit which in the U.S. may or may not have an aeration pump in it).

Newer U.S. septic systems may have a vent riser pipe some distance from the house but that is usually 2 to 3 feet instead of 15 feet high. At any rate I would not expect odors from it to be noticeable inside the house. Also, vent risers originating from drain pipes in the house and going through the roof usually do not result in odors inside the house.

All septic systems require maintenance, including (every few years) pumping out the fermentation chamber and removing the sludge (bottom layer) and grease (top layer). If these materials are allowed to accumulate indefinitely then the seepage pit or leach field will become impregnated by these materials and cease to absorb liquid and have to be dug up and relaid which is very expensive.
 

Last edited by AllanJ; 07-06-16 at 08:38 PM.
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Old 07-07-16, 04:07 AM
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Originally Posted by lhpdiver
". . . There are no vents on top of the house for this system . . ."
What substitutes as the alternative . . . . just the floor drains ?

Maybe somewhere you have a hidden internal vacuum breaker, or Air Admittance Vent,with a spring loaded flapper at the top, which has fatigued over the past 20 years and is now allowing sewer gases to enter the living quarters ?

https://www.plumbingsupply.com/autovent.html
 
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Old 07-07-16, 04:39 AM
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I can certainly try adding water regularly to the floor drains - but once again I really feel that if it never rained here we would never have odors in the bathroom. In three months there will be no more odors - and I will not need to add water to the drains.

In the US - what would happen if you capped off the 'vent riser pipe' ? In a sense I think that may be what has happened with all the rain. That pipe also sat behind a massive bougainvillea hedge (lots of leaves/flowers which may have fallen in over time). I have cut the hedge back.

This system is as far away from the house as it could be (perhaps 60-80 ft away). Other than that 'pipe' there is nothing above ground. As I said the pipe is about 15 ft tall. Beneath that area of the yard is another 30 ft tall retaining wall which drops down to a wooded lot - so there is plenty of room for seepage.

We do have a friend with a beautiful 5 year old house and she needed to rebuild her septic system - and it was costly. But costly here is not the same as costly in the US. Perhaps the cost of maintenance is the same/near the cost of repair ? I'll have to ask her but I believe our friend still now has no intention of 'maintaining' her septic system.

Does a US system need the roof vents because floors generally don't have readily accessible drains ? Do they serve the same purpose ?
 
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Old 07-07-16, 08:25 AM
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My wife had brief phone call with our friend with the new septic system. Her problem was caused by her lines being too small for her house. She said around here the odors are not at all uncommon in the rainy season and that the only thing she does is periodically throw some sort of yeast like substance down her drains (she gets it at HomeDepot). fwiw - she does have a phd in chemistry...
 
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Old 07-09-16, 08:59 AM
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Whose problem was caused by whose lines being too small for whose house?

All drain systems require some vent beyond the traps and going to the outside. Otherwise some fixtures can gurgle when you use other fixtures, or the fixture you are using just does not work as well as it should. With no downstream venting, toilets might not flush completely or properly.

Sometimes with a septic system there is a continuous open path from the house drain pipes through a septic tank and out to the leach field and up the 2' riser (in the U.S.) or your 15' riser to the outside; other times water levels may be too high and choke off this path.

U.S. building codes require additional vent pipes in the house plumbing to almost guarantee an open path at all times.
 

Last edited by AllanJ; 07-09-16 at 09:21 AM.
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Old 07-09-16, 09:05 AM
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Our neighbor - who had a backup and had to replace her 5 year old septic system.

I've been adding about a gallon of water to the floor drain in the bathroom. I think it is making a difference - but it has not rained in 4-5 days also. As I said that drain is conical. I may cut a piece of 1.5" PVC and insert into the drain's water.
 
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Old 12-16-17, 12:54 PM
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Sorry for this late post. I was searching for another post I made a while back and came across this thread.

Well the septic odors in the house were definitely caused by our septic system. In perhaps March we started digging We found a waste line and followed it along. It was perhaps 2 feet deep and in several areas was totally crushed - cheap PVC. At some point we came across a 'register' (trap) which was in pretty good shape because for years (?) nothing ever reached it. Next we found two 1100 liter tanks (connected by 3" PVC. They were filled to the gills with waste. The first tank was pretty much rock solid. The second tank was mostly stale liquid. But the PVC which had connected the two tanks had shifted and there was no longer a connection. Further along we found a large pit, perhaps 15 feet deep and 15 feet round. It was bone dry.

So we replaced all the cheap PVC - had the two tanks properly connected - securing the PVC with cement. We had the tanks pumped out. We have made it through the latest rainy season and we had no more odors.
 
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Old 12-16-17, 01:44 PM
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You can use this link to locate your old posts....
https://www.doityourself.com/forum/s...earchid=660294
 
 

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