Ask an Expert about Mobile Home Venting Issues and Sewer Smells

Today’s article is the first of a new series we’re starting called Ask a Mobile Home Expert. We’ll be covering mobile home venting issues and sewer smells that can occur when your ventilation system isn’t working properly.

Since I began Mobile Home Living in 2011, we have published over 500 articles and received over 6,000 mobile home-related questions and comments. I’m proud to say that I have personally replied to every single question! In several cases, I was able to get an expert to answer the questions (being married to a licensed master plumber/contractor has its perks). That’s how we got the idea for this new Ask a Mobile Home Expert Series.

 

plumbing ventilation system diagram - Ask an Expert about Mobile Home Venting Issues
A basic portrayal of a ventilation system. Source: Pinterest

 

Mobile Home Venting Issues are Extremely Common

Your mobile home venting system is more important than most of us realize. Every plumbing system has 3 parts: the supply line where the water comes from, the drain lines where the waste goes, and the ventilation lines that allow the system to breathe and pushes the sewer smells up and away from the home.

Mobile home venting systems are pretty cool! The way it all works together to create a happy and healthy home is neat. Imagine if we had to live with our sewage smells – what an awful thought! Here are a few scenarios where homeowners were dealing with mobile home venting issues.

 

Washing Machine Sewer Smells

We are having a sewage odor problem that comes and goes. It’s worse in the laundry room and since the air conditioner unit is close the smell gets distributed all over the house. We have a brand new septic system (only 1-year-old) and only the kitchen and the toilets drain to the septic system. Everything else drains to the backyard as gray water. There is no odor where the gray water drains, and there is no odor under the house. A plumber fixed the ventilation stack about 9 months ago and within about 2 weeks we had no more odor problems until about 3 weeks ago. Since then, the plumber has come back out, but we are still getting the smell. Any ideas?

We have a brand new septic system (only 1-year-old) and only the kitchen and the toilets drain to the septic system. Everything else drains to the backyard as gray water. There is no odor where the gray water drains, and there is no odor under the house. A plumber fixed the ventilation stack about 9 months ago and within about 2 weeks we had no more odor problems until about 3 weeks ago. Since then, the plumber has come back out, but we are still getting the smell. Any ideas?

There is no odor where the gray water drains, and there is no odor under the house. A plumber fixed the ventilation stack about 9 months ago and within about 2 weeks we had no more odor problems until about 3 weeks ago. Since then, the plumber has come back out, but we are still getting the smell. Any ideas?

 

It sounds like the water in your p-trap is getting siphoned out of washer drain. If that isn’t the culprit, check to see if the AC unit drain is tied into the sewer. If it is it will need to be disconnected as it doesn’t have a p-trap and will allow the odor to escape.

 

washing machine p-trap diagram - mobile home venting issues and sewer smells - Ask a Mobile Home Expert Series

Sometimes, negative pressure can siphon the water 
out and allow sewage smells to come into the house.

Image source.

 

 

Can Mobile Home Ventilation Lines Have Elbows?

We have a sewer smell in our bathroom and bedroom. I checked ventilation pipe that extends through the roof. Can a ventilation pipe have an L-shaped pipe? I put a wire down pipe and hit something hard about 12 to 18 inches down.

Yes, your vent stack will usually include elbows. A vent elbow can be a complete 90 degrees whereas your water line elbows have a curve instead of a corner.

If you have a stoppage you’ll definitely want to get that cleared, that’s probably your problem. The system has to be able to breathe. You could try pouring water down the vent to see if it’s a clog. If it’s an elbow it will drain, if it’s a clog it will backflow.

 mobile home venting issues and sewer smells - Ask a Mobile Home Expert Series - elbow shown in vent line

 This diagram shows a 90-degree elbow in the vent line.

Washer Drains into Bathtub in Mobile Home 

We invested in a 2004 Fortune double wide home, it has two bathrooms, a master, and the guest. The other day I took a shower and we did the dishes and everything was fine,  with great drainage. However, my fiance did a load of laundry and when it when into its spin/drain cycle all that water started coming up into both tubs!

It left about 2-3 inches of water in them and you could tell it was dirty laundry water, they didn’t drain at all for almost 10 hours. Also, the water in the toilets is gone, I took the lid off of the toilet and let some water into the toilet bowl and as that water went into the toilet bowl you could see the water rising inside the tub.

Yet, the kitchen sink doesn’t seem to be affected or to affect anything at all. I have searched and searched for answers. Help!

It sounds like you have a stoppage. As a result, this would make the drains slow since you aren’t getting the pressure equalized in your traps so it’s pulling into your toilets.

You probably happened to use just enough water to fill the trunk line up until it came out of tub drains. The water gets sucked out of the toilets because the trunk is full of water so it cuts off the toilet’s ventilation which siphons out the toilet.

You’ll need to find where the clog is and snake it out. You can try a residential snake available at Amazon here (affiliate link) but sometimes it takes an industrial snake that shoots high-pressure water so you’ll need to hire a plumber.

 mobile home venting issues and sewer smells - Ask a Mobile Home Expert Series - residential snake

Slow Drains in a Mobile Home

I am renting a manufactured home that has several previous renters. I started experiencing very slow draining & backing up in my kitchen sink. I’ve tried Draino, snaking & plunging it, taking the pipes apart & cleaning them; nothing worked.

I loosened the air admittance valve cap & the water drained perfectly. I cleaned the vent stack thinking that may help. As soon as I tightened the valve cap back up the sink stopped up again. Finally, I loosened the cap again & the sink is draining just fine. Could I need a new air admittance valve cap?

Yep! An auto vent is a continuously working mechanism that opens and closes on demand. It sounds like it is just worn out.

They are around $25 at your local home improvement store or order one from Amazon here (affiliate link).
Studor Vent - mobile home venting issues and sewer smells - Ask a Mobile Home Expert Series

Have More Questions about Mobile Home Venting Issues or Smells?

These questions are good representations of the average mobile home venting issues and sewer smells that can occur in the typical home but there’s a lot more to it.

Also, be sure to check out next week’s Ask a Mobile Home Expert article as we continue to answer your mobile home plumbing questions!

As always, thanks for reading Mobile Home Living!

 

Disclosure: Any answers to questions posed and any recommendations or information provided herein should not be used as a substitute of an expert or any relevant professional that has inspected the issues in person. 

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6 Comments
  1. Cindy Walker says

    Drainage problem with the washing machine and kitchen sink. The drain pie was cut and drains on the dirt on the side of the mobile home by the kitchen. It’s flooded all the time. It gets under the house too. The rain makes it worse. I saw a 3″ x50′ corregated drain pipe at Lowe’s for $29. Can I attach that to extend it out into the property to drain out there to move the water away from the house? Do you have any other suggestions? What are the possible damages this may have caused already? The place looks bad and is falling apart. Thank you.

    1. Crystal Adkins says

      Absolutely! A true ditch with a metal grate is also a good idea. This will keep cars from crushing it too. We have a couple across our driveway for rain diversion – all we do is clean the culvert/ditch out every couple of months.

      Best of luck!

  2. Thomas says

    I bought a 95 manufactured home double wide. It has what I call a “fresh air fan” in the family room ceiling that is operated by a switch on the wall. When I bought the home the fan assembly and motor was missing and I cannot find a replacement anywhere. The fan vents straight up thru a roof vent. I would like to find a replacement motor and fan assembly or a similar size top venting fan so I do not have to replace drywall. Do you know where I could find a replacement, I can only seem to find bathroom fans. I have had these in my homes before so I know there are commonly installed. Just not commonly found to replace.

    1. Crystal Adkins says

      Hi Thomas,

      Unfortunately, I am not very knowledgeable about HVAC or electrical. I did Google a bit and found that Broan seems to be the biggest supplier of energy recovery ventilation and fresh-air systems. Their website is Broan.com.

      I also found this page from the Energy.gov: https://energy.gov/energysaver/whole-house-ventilation

      Best of luck!

  3. Charlotte says

    Hi, we just bought one of those great craigslist mobile home finds. We are going to be remodeling throughout. It has an island range with a range hood over it, and I’d love to customize it to a farmhouse look. Is it possible to hang a heavier hood cover in a mobile home? I’d hate to pull the roof down on us. Right now it is basic generic straight hood cover. I would love to do something like this. http://2.bp.blogspot.com/-tJpNKvY2F38/U8350Rwg5MI/AAAAAAAAN3s/H8harB8QY2I/s1600/hood.jpg

    Thanks!

    1. Crystal Adkins says

      Hi Charlote,

      A nice hood really does make a kitchen stand out! Great idea! You shouldn’t have any problems as long as the hood isn’t too heavy – just make sure it is secured into studs. I’ve seen a homeowner build their own hood cover just like that with mdf (or maybe it was thin pine board) and trim.

      Best of luck!