Horrible smell from under my trailer not propane

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SoloCamper

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Hi everyone. I am at my wits end so joined this great community. I have a 2013 Sierra fifth wheel with 1.5 bathrooms. There is an awful smell coming from under my trailer. A few weeks back the smell was inside my trailer but after hours of internet searching I realized it was my air admittance valve. That was a cheap easy fix after becoming a contortionist to do it. The smell was gone for a week both inside and outside the trailer. Now it is only under my trailer that has started to smell. First thinking it was propane, even though I didn't have it turned on I lit the stove removing all gas in the lines and disconnected the tank. The smell persisted. Our campground repair guy came out and said it was the septic. I was leaking a small amount from the back grey line. He readjusted it and tightened it and said I was good to go. Nope! The front black shows no leakage. The front grey pull is unfortunately broken but the tank has empty for years now. When there is a breeze you cannot smell anything but when there isn't, oh my! It smells from the back of my trailer and to my deck in the front where I work. It is nauseating! What can I check? What could it be? Please any help is welcome!!
 

Kirk

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Are you sure that the odor is from the RV and not coming back up from the septic system? It is quite normal for a septic system to have sewer gas in the lines and it may be venting from there under your RV.
 

Kevin Means

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If you're not sure what is causing the odor, you might want to take a look at your batteries. Many years ago. we had one of our batteries go bad, and the odor was overwhelming. I initially thought it was a propane leak but it turned out to be the battery.

Kev
 

SoloCamper

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Mass
The odor is definitely septic.
Kirk, I am unsure as it is only my trailer is it is coming back up from the septic system.
SeilBird, I have been parked here five years. I never leave my black tanks open.
Kevin Means yes I checked the batteries as mine did go bad one year as well. That compartment smells fine and the battery is good. you are correct though that odor was bad.

I did just have someone stop by telling me to fill and flush my black tank a few times. He said he is almost certain it may be the "dreaded poop pyramid".....ugh. I have evaded that for 9 years so far. I just filled the tank up once and the odor is stronger than earlier. There was a breeze but I had dumped it once. I will do it a few more times too see.
Hopefully that is the problem and not a cracked pipe or something going to the septic!

 

Old_Crow

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I added those venturi caps to the vents for my holding tanks. This cured the problem of odor inside the coach when I'm moving but created an unintentional 2nd problem. If I open the roof vent in the water closet and the wind is in the proper direction, the smell from the black tank vent (which is less than 2' from the WC vent) comes through the roof vent.
Is it possible that the smell is actually coming out of the roof vent and sort of settling?
 

SoloCamper

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Mass
Old_Crow the smell is defiantly from the underneath of the trailer. I have flushed it twice now. The odd thing is that when it is filling it smells. When I dump it, the smell goes away for a little while then comes back when I put water back in. Fearing the "dreaded poop pyramid" I stuck a broom stick down to try and shake things up but I hit pipes??? I am not hitting the bottom of the tank and if I am it's quite shallow and not a Pile of anything. It's dark so I gave up for the night but if I am hitting potentially pipes, what good would a wand do? I also do not know what vents you are talking about for holding tanks. I did put a new Redi-Vent PVC adapter valve on a few weeks ago under my kitchen sink outside in the fridge compartment because that the most horrid smell both inside and out and it worked. I am also seasonal and only had to move last fall because they doubled my site width so I do not travel. I simply moved 25' backwards.
I also discovered that when I push the buttons to see if the tanks are full, I need to flip a switch to see one black tank which is my primary. (Never knew this before) That tank says full but I can continuously fill the tank for about 15+ minutes with water and it flushes into the septic as if it is only liquid in there.
SpencerPJ, I almost at this point wish it was a dead animal that may be easier to trace! And eventually the smell would dissipate.
I appreciate all the comments, hopefully we get to the bottom (maybe literally) of this soon!!!
 

Old_Crow

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Some RV toilets dump straight down into the top of the tank. Those are the easy ones that you can open the toilet valve and actually see the level in the holding tank with a flashlight and probe them with a wand or a stick. Others are like mine and dump into a horizontal pipe that leads to the tank. On mine I can't see the level in the tank until it's full enough to back up into that pipe.

I assume (yeah, I know) you are parked on a dirt surface, so you can't really tell if it's leaking or not. You might go to a Home Depot or Lowe's and see if you can score some big sheets of old cardboard that you can lay under the rig for a couple of days. That might help you spot signs of a leak.
 

Kirk

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That was a cheap easy fix after becoming a contortionist to do it. The smell was gone for a week both inside and outside the trailer.
Have you considered that the odor now might be from the gray water tank and not the black? If the plumbing vent replacement stopped the same odor inside and that is for the gray tank, maybe you are working on the wrong tank? Since you arent traveling to agitate the tank with a detergent and water in it, I would suggest that you try a mix of TSP cleaner that is mixed like you would clean with but with enough to at least half fill the tank to be cleaned and then let it sit and soak for several hours before you dump it. Even without agitation is will soak and is particularly good for any greasy residue.
1660751332829.png
 

SeilerBird

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St Cloud Florida USA
The odor is definitely septic.
Kirk, I am unsure as it is only my trailer is it is coming back up from the septic system.
SeilBird, I have been parked here five years. I never leave my black tanks open.
Kevin Means yes I checked the batteries as mine did go bad one year as well. That compartment smells fine and the battery is good. you are correct though that odor was bad.

I did just have someone stop by telling me to fill and flush my black tank a few times. He said he is almost certain it may be the "dreaded poop pyramid".....ugh. I have evaded that for 9 years so far. I just filled the tank up once and the odor is stronger than earlier. There was a breeze but I had dumped it once. I will do it a few more times too see.
Hopefully that is the problem and not a cracked pipe or something going to the septic!

A lot of water will not cure the dreaded poop pyramid. Neither will most chemicals. They become as hard as a rock. You should try a small camera like this to see what is going on in your black tank.

 

SMR

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see if you can lower a small section of the sewer hose to create a p trap and see if that helps. Also make sure there are no holes or tears in the sewer hose.
 

Kirk

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P-Trap.jpg

See post immediately above, as in P trap.
 

SoloCamper

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Mass
Old_Crow I will try cardboard I have plenty to burn!

Kirk I have put so many chemicals down there it has to be the black. I continue to watch videos and came across this today.

Unique RV Digest-It Black Holding Tank Treatment - Concentrated Liquid Toilet Treatment - Eliminates Odors, Breaks Down Waste​

I just ordered some and will try when I return Friday. It also says for grey tanks so I will put some down there also.

SMR and Kirk I am hard piped in. There are sufficient dips where there should be. I also made sure to relevel and block them better the other day for drainage just in case.
 

SoloCamper

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Mass
SeilerBird now that just looks like something I want! Even if it doesn't help with this problem I just ordered one!! It should be in by Friday so hopefully before I go up, so I can check it out inside there! Have you used this one before?
Thank you
 

SeilerBird

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SeilerBird now that just looks like something I want! Even if it doesn't help with this problem I just ordered one!! It should be in by Friday so hopefully before I go up, so I can check it out inside there! Have you used this one before?
Thank you
I own one but never needed it on any of my RVs. Only one I bought came with a free poop pyramid and I could see it by looking down the drain in the bottom of the toilet. I tried several things to get rid of it but brute force was the only thing that worked. Took a lot of water pressure on the top of the pile.
 

SoloCamper

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Joined
Aug 16, 2022
Posts
12
Location
Mass
I own one but never needed it on any of my RVs. Only one I bought came with a free poop pyramid and I could see it by looking down the drain in the bottom of the toilet. I tried several things to get rid of it but brute force was the only thing that worked. Took a lot of water pressure on the top of the pile.
Unfortunately my tank doesn't go straight down. Brute force seems tricky with this set up.
 

SeilerBird

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St Cloud Florida USA

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